https://leettube.dev 2026-10-06T15:35:40.725Z weekly 1 https://leettube.dev/about monthly 0.5 https://leettube.dev/worlds/warm-up 2026-10-06T15:35:40.725Z weekly 0.9 https://leettube.dev/worlds/arrays 2026-10-06T15:35:40.725Z weekly 0.9 https://leettube.dev/worlds/trees 2026-10-06T15:35:40.725Z weekly 0.9 https://leettube.dev/worlds/backtracking 2026-10-06T15:35:40.725Z weekly 0.9 https://leettube.dev/worlds/dynamic-programming 2026-10-06T15:35:40.725Z weekly 0.9 https://leettube.dev/worlds/graphs 2026-10-06T15:35:40.725Z weekly 0.9 https://leettube.dev/worlds/greedy 2026-10-06T15:35:40.725Z weekly 0.9 https://leettube.dev/worlds/bits-and-math 2026-10-06T15:35:40.725Z weekly 0.9 https://leettube.dev/worlds/design 2026-10-06T15:35:40.725Z weekly 0.9 https://leettube.dev/watch/intro-warm-up Warm-up tutorial https://leettube.dev/posters/intro-warm-up.jpg Before the first stage: how the work grows as the input grows, and the hash map, which answers "have I seen this?" in one hop. https://leettube.dev/api/video/intro-warm-up.mp4 45 2026-10-05T21:56:10.668Z 2026-10-05T21:56:10.668Z monthly 0.8 https://leettube.dev/watch/two-sum Two Sum (LeetCode 1) https://leettube.dev/posters/two-sum.jpg Find the two numbers that add up to the target. Walk once, and for each number look up the partner you need in a map of what you've seen. https://leettube.dev/api/video/two-sum.mp4 64 2026-10-05T21:56:20.732Z 2026-10-05T21:56:20.732Z monthly 0.8 https://leettube.dev/watch/valid-parentheses Valid Parentheses (LeetCode 20) https://leettube.dev/posters/valid-parentheses.jpg Check that every bracket is closed by the right type, in the right order. Push each opener, and match each closer against the top of the stack. https://leettube.dev/api/video/valid-parentheses.mp4 96 2026-10-05T21:56:21.351Z 2026-10-05T21:56:21.351Z monthly 0.8 https://leettube.dev/watch/binary-search Binary Search (LeetCode 704) https://leettube.dev/posters/binary-search.jpg Find a target in a sorted list. Check the middle and throw away the half that can't hold it, so each step halves the search. https://leettube.dev/api/video/binary-search.mp4 99 2026-10-05T21:56:04.813Z 2026-10-05T21:56:04.813Z monthly 0.8 https://leettube.dev/watch/linked-list-cycle Linked List Cycle (LeetCode 141) https://leettube.dev/posters/linked-list-cycle.jpg Does the list loop back on itself? Send a tortoise and a hare down it: if there's a cycle, the faster runner must catch the slower one. https://leettube.dev/api/video/linked-list-cycle.mp4 85 2026-10-05T21:56:12.317Z 2026-10-05T21:56:12.317Z monthly 0.8 https://leettube.dev/watch/intersection-of-two-linked-lists Intersection of Two Linked Lists (LeetCode 160) https://leettube.dev/posters/intersection-of-two-linked-lists.jpg Find the node where two lists join: walk each list, switch to the other head at the end, and both runners meet at the join. https://leettube.dev/api/video/intersection-of-two-linked-lists.mp4 98 2026-10-06T12:21:37.442Z 2026-10-06T12:21:37.442Z monthly 0.8 https://leettube.dev/watch/find-the-duplicate-number Find the Duplicate Number (LeetCode 287) https://leettube.dev/posters/find-the-duplicate-number.jpg n + 1 numbers in 1..n, one repeated. Treat each value as a pointer to an index: the duplicate starts a cycle, and fast and slow runners find it. https://leettube.dev/api/video/find-the-duplicate-number.mp4 97 2026-10-06T09:36:10.111Z 2026-10-06T09:36:10.111Z monthly 0.8 https://leettube.dev/watch/reverse-linked-list Reverse Linked List (LeetCode 206) https://leettube.dev/posters/reverse-linked-list.jpg Turn every arrow of a linked list around in place. Keep three pointers: save next, flip current back to previous, step forward. https://leettube.dev/api/video/reverse-linked-list.mp4 96 2026-10-05T21:56:18.067Z 2026-10-05T21:56:18.067Z monthly 0.8 https://leettube.dev/watch/merge-two-sorted-lists Merge Two Sorted Lists (LeetCode 21) https://leettube.dev/posters/merge-two-sorted-lists.jpg Splice two sorted lists into one. Keep a tail pointer behind a dummy head and always take the smaller front node. https://leettube.dev/api/video/merge-two-sorted-lists.mp4 86 2026-10-05T21:56:14.369Z 2026-10-05T21:56:14.369Z monthly 0.8 https://leettube.dev/watch/reorder-list Reorder List (LeetCode 143) https://leettube.dev/posters/reorder-list.jpg Weave a linked list first, last, second, second to last. Find the middle with slow and fast pointers, reverse the back half, then merge. https://leettube.dev/api/video/reorder-list.mp4 98 2026-10-06T01:54:38.690Z 2026-10-06T01:54:38.690Z monthly 0.8 https://leettube.dev/watch/palindrome-linked-list Palindrome Linked List (LeetCode 234) https://leettube.dev/posters/palindrome-linked-list.jpg Does a linked list read the same both ways? Find the middle with fast and slow runners, reverse the back half, then compare the halves node by node. https://leettube.dev/api/video/palindrome-linked-list.mp4 98 2026-10-06T09:11:05.817Z 2026-10-06T09:11:05.817Z monthly 0.8 https://leettube.dev/watch/remove-nth-node-from-end-of-list Remove Nth Node From End of List (LeetCode 19) https://leettube.dev/posters/remove-nth-node-from-end-of-list.jpg Remove the nth node from the end in one pass: start a fast runner n steps ahead, move both until it falls off, then unlink the next node. https://leettube.dev/api/video/remove-nth-node-from-end-of-list.mp4 98 2026-10-06T05:21:54.321Z 2026-10-06T05:21:54.321Z monthly 0.8 https://leettube.dev/watch/add-two-numbers Add Two Numbers (LeetCode 2) https://leettube.dev/posters/add-two-numbers.jpg Two numbers stored as reversed linked lists: walk both at once, add digit by digit like on paper, and carry the 1 into the next node. https://leettube.dev/api/video/add-two-numbers.mp4 98 2026-10-06T05:24:01.311Z 2026-10-06T05:24:01.311Z monthly 0.8 https://leettube.dev/watch/contains-duplicate Contains Duplicate (LeetCode 217) https://leettube.dev/posters/contains-duplicate.jpg Does any number show up twice? Walk the list once with a set of values you've already seen, and stop the moment one repeats. https://leettube.dev/api/video/contains-duplicate.mp4 82 2026-10-05T21:56:06.784Z 2026-10-05T21:56:06.784Z monthly 0.8 https://leettube.dev/watch/valid-anagram Valid Anagram (LeetCode 242) https://leettube.dev/posters/valid-anagram.jpg Check if two words use exactly the same letters. Count up for every letter in one, count down for the other, and see if every tally hits zero. https://leettube.dev/api/video/valid-anagram.mp4 89 2026-10-05T21:56:21.497Z 2026-10-05T21:56:21.497Z monthly 0.8 https://leettube.dev/watch/ransom-note Ransom Note (LeetCode 383) https://leettube.dev/posters/ransom-note.jpg Can the note be cut from the magazine? Count every magazine letter, then spend one per note letter and fail the moment a count runs out. https://leettube.dev/api/video/ransom-note.mp4 99 2026-10-06T15:15:28.802Z 2026-10-06T15:15:28.802Z monthly 0.8 https://leettube.dev/watch/valid-palindrome Valid Palindrome (LeetCode 125) https://leettube.dev/posters/valid-palindrome.jpg Check if a phrase reads the same both ways, ignoring case and punctuation. Walk in from both ends, skip the junk, and compare letters. https://leettube.dev/api/video/valid-palindrome.mp4 93 2026-10-06T00:53:14.725Z 2026-10-06T00:53:14.725Z monthly 0.8 https://leettube.dev/watch/roman-to-integer Roman to Integer (LeetCode 13) https://leettube.dev/posters/roman-to-integer.jpg Turn a Roman numeral into a number. Look up each letter's value and add it, unless the next letter is bigger, then subtract it. https://leettube.dev/api/video/roman-to-integer.mp4 109 2026-10-06T01:18:24.122Z 2026-10-06T01:18:24.122Z monthly 0.8 https://leettube.dev/watch/intro-arrays Arrays tutorial https://leettube.dev/posters/intro-arrays.jpg Walk the array once with a little state instead of restarting everywhere: two pointers closing in from the ends, or a window that grows on the right and shrinks on the left. https://leettube.dev/api/video/intro-arrays.mp4 43 2026-10-05T21:56:09.639Z 2026-10-05T21:56:09.639Z monthly 0.8 https://leettube.dev/watch/best-time-to-buy-stock Best Time to Buy and Sell Stock (LeetCode 121) https://leettube.dev/posters/best-time-to-buy-stock.jpg Buy one day, sell on a later day, for the biggest profit. Walk the prices once, remembering the cheapest day so far. https://leettube.dev/api/video/best-time-to-buy-stock.mp4 92 2026-10-05T21:56:04.815Z 2026-10-05T21:56:04.815Z monthly 0.8 https://leettube.dev/watch/merge-intervals Merge Intervals (LeetCode 56) https://leettube.dev/posters/merge-intervals.jpg Merge every overlapping interval. Sort by start, then either extend the last merged interval or start a new one. https://leettube.dev/api/video/merge-intervals.mp4 99 2026-10-05T21:56:14.064Z 2026-10-05T21:56:14.064Z monthly 0.8 https://leettube.dev/watch/group-anagrams Group Anagrams (LeetCode 49) https://leettube.dev/posters/group-anagrams.jpg Group words that are anagrams of each other. Sort each word's letters into a key, then file every word under its key in a hash map. https://leettube.dev/api/video/group-anagrams.mp4 94 2026-10-05T21:56:08.439Z 2026-10-05T21:56:08.439Z monthly 0.8 https://leettube.dev/watch/top-k-frequent Top K Frequent (LeetCode 347) https://leettube.dev/posters/top-k-frequent.jpg Find the k values that appear most often. Tally them in a map, then keep a k-spot leaderboard in a min-heap instead of sorting everything. https://leettube.dev/api/video/top-k-frequent.mp4 92 2026-10-05T21:56:20.257Z 2026-10-05T21:56:20.257Z monthly 0.8 https://leettube.dev/watch/longest-consecutive-sequence Longest Consecutive Sequence (LeetCode 128) https://leettube.dev/posters/longest-consecutive-sequence.jpg Find the longest run of consecutive numbers in an unsorted list. Put them in a set, and only count up from numbers with no left neighbour. https://leettube.dev/api/video/longest-consecutive-sequence.mp4 95 2026-10-06T01:47:25.049Z 2026-10-06T01:47:25.049Z monthly 0.8 https://leettube.dev/watch/longest-substring Longest Substring (LeetCode 3) https://leettube.dev/posters/longest-substring.jpg Find the longest run of characters with no repeats. Slide a window along the string, and when a letter repeats, jump the left edge past its last copy. https://leettube.dev/api/video/longest-substring.mp4 95 2026-10-05T21:56:13.082Z 2026-10-05T21:56:13.082Z monthly 0.8 https://leettube.dev/watch/minimum-window-substring Minimum Window Substring (LeetCode 76) https://leettube.dev/posters/minimum-window-substring.jpg Find the shortest stretch of s holding every letter of t. Grow the window right until it's complete, then shrink from the left while it stays so. https://leettube.dev/api/video/minimum-window-substring.mp4 102 2026-10-05T21:56:15.432Z 2026-10-05T21:56:15.432Z monthly 0.8 https://leettube.dev/watch/sliding-window-maximum Sliding Window Maximum (LeetCode 239) https://leettube.dev/posters/sliding-window-maximum.jpg Report the biggest number in every window of k as it slides. Keep a deque of shrinking values, so the front is always the max. https://leettube.dev/api/video/sliding-window-maximum.mp4 97 2026-10-06T02:20:59.375Z 2026-10-06T02:20:59.375Z monthly 0.8 https://leettube.dev/watch/subarray-sum-equals-k Subarray Sum Equals K (LeetCode 560) https://leettube.dev/posters/subarray-sum-equals-k.jpg Count the stretches of numbers that add up to k, negatives included. Keep a running total and a tally of totals seen, and look up the one that's k behind. https://leettube.dev/api/video/subarray-sum-equals-k.mp4 95 2026-10-05T21:56:19.309Z 2026-10-05T21:56:19.309Z monthly 0.8 https://leettube.dev/watch/product-except-self Product of Array Except Self (LeetCode 238) https://leettube.dev/posters/product-except-self.jpg Each spot gets the product of every other number, without division. Multiply everything to its left by everything to its right in two passes. https://leettube.dev/api/video/product-except-self.mp4 102 2026-10-05T21:56:17.695Z 2026-10-05T21:56:17.695Z monthly 0.8 https://leettube.dev/watch/3sum 3Sum (LeetCode 15) https://leettube.dev/posters/3sum.jpg Find every triple that sums to zero, with no repeats. Sort, fix one number, then close in from both ends with two pointers. https://leettube.dev/api/video/3sum.mp4 105 2026-10-05T21:56:04.697Z 2026-10-05T21:56:04.697Z monthly 0.8 https://leettube.dev/watch/container-with-most-water Container With Most Water (LeetCode 11) https://leettube.dev/posters/container-with-most-water.jpg Pick two walls that hold the most water. Start at both ends and always move the shorter wall inward, since it caps the area. https://leettube.dev/api/video/container-with-most-water.mp4 102 2026-10-05T21:56:06.537Z 2026-10-05T21:56:06.537Z monthly 0.8 https://leettube.dev/watch/sort-colors Sort Colors (LeetCode 75) https://leettube.dev/posters/sort-colors.jpg Sort an array of 0s, 1s and 2s in one pass: three pointers sweep zeros to the front and twos to the back, leaving ones in the middle. https://leettube.dev/api/video/sort-colors.mp4 103 2026-10-06T15:35:40.725Z 2026-10-06T15:35:40.725Z monthly 0.8 https://leettube.dev/watch/evaluate-reverse-polish-notation Evaluate Reverse Polish Notation (LeetCode 150) https://leettube.dev/posters/evaluate-reverse-polish-notation.jpg Work out an expression written with operators after their numbers. Push each number on a stack; each operator pops two and pushes the result. https://leettube.dev/api/video/evaluate-reverse-polish-notation.mp4 116 2026-10-06T03:57:09.077Z 2026-10-06T03:57:09.077Z monthly 0.8 https://leettube.dev/watch/daily-temperatures Daily Temperatures (LeetCode 739) https://leettube.dev/posters/daily-temperatures.jpg For each day, count the wait until a warmer one. Keep a stack of days still waiting; a warm day pops every colder day below it. https://leettube.dev/api/video/daily-temperatures.mp4 108 2026-10-06T02:25:20.768Z 2026-10-06T02:25:20.768Z monthly 0.8 https://leettube.dev/watch/trapping-rain-water Trapping Rain Water (LeetCode 42) https://leettube.dev/posters/trapping-rain-water.jpg How much rain pools between the bars? Walk in from both ends, always moving the side with the lower wall, whose water is already decided. https://leettube.dev/api/video/trapping-rain-water.mp4 95 2026-10-05T21:56:20.329Z 2026-10-05T21:56:20.329Z monthly 0.8 https://leettube.dev/watch/largest-rectangle Largest Rectangle in Histogram (LeetCode 84) https://leettube.dev/posters/largest-rectangle.jpg The biggest rectangle under a histogram. Keep a stack of rising bars, and when a shorter bar arrives, pop and measure each taller one. https://leettube.dev/api/video/largest-rectangle.mp4 95 2026-10-05T21:56:12.296Z 2026-10-05T21:56:12.296Z monthly 0.8 https://leettube.dev/watch/search-in-rotated-sorted-array Search in Rotated Sorted Array (LeetCode 33) https://leettube.dev/posters/search-in-rotated-sorted-array.jpg A sorted list was rotated, yet binary search still works: one half is always in order, so check if the target sits there and drop the other. https://leettube.dev/api/video/search-in-rotated-sorted-array.mp4 95 2026-10-06T05:16:56.171Z 2026-10-06T05:16:56.171Z monthly 0.8 https://leettube.dev/watch/median-of-two-sorted-arrays Median of Two Sorted Arrays (LeetCode 4) https://leettube.dev/posters/median-of-two-sorted-arrays.jpg Find the median of two sorted arrays in log time. Binary search a cut in the shorter one so both left halves hold the smaller half. https://leettube.dev/api/video/median-of-two-sorted-arrays.mp4 104 2026-10-06T01:50:32.862Z 2026-10-06T01:50:32.862Z monthly 0.8 https://leettube.dev/watch/intro-trees Trees tutorial https://leettube.dev/posters/intro-trees.jpg Trust each child to answer, then combine the answers at the node. A missing child is the base case, and three lines of code solve most tree problems. https://leettube.dev/api/video/intro-trees.mp4 45 2026-10-05T21:56:10.462Z 2026-10-05T21:56:10.462Z monthly 0.8 https://leettube.dev/watch/invert-binary-tree Invert Binary Tree (LeetCode 226) https://leettube.dev/posters/invert-binary-tree.jpg Mirror a binary tree. Swap a node's two children, then do the same to each child, all the way down. https://leettube.dev/api/video/invert-binary-tree.mp4 88 2026-10-05T21:56:11.154Z 2026-10-05T21:56:11.154Z monthly 0.8 https://leettube.dev/watch/maximum-depth Maximum Depth of Binary Tree (LeetCode 104) https://leettube.dev/posters/maximum-depth.jpg How deep does a binary tree go? Ask each child for its depth, take the bigger one and add one for yourself. https://leettube.dev/api/video/maximum-depth.mp4 89 2026-10-05T21:56:13.534Z 2026-10-05T21:56:13.534Z monthly 0.8 https://leettube.dev/watch/same-tree Same Tree (LeetCode 100) https://leettube.dev/posters/same-tree.jpg Are two binary trees identical? Compare the two roots, then trust recursion to compare the left pair and the right pair. A mismatch anywhere ends it. https://leettube.dev/api/video/same-tree.mp4 102 2026-10-06T05:19:41.152Z 2026-10-06T05:19:41.152Z monthly 0.8 https://leettube.dev/watch/symmetric-tree Symmetric Tree (LeetCode 101) https://leettube.dev/posters/symmetric-tree.jpg Is a binary tree its own mirror? Compare the left and right subtrees in pairs: outer with outer, inner with inner, all the way down. https://leettube.dev/api/video/symmetric-tree.mp4 95 2026-10-06T14:28:52.219Z 2026-10-06T14:28:52.219Z monthly 0.8 https://leettube.dev/watch/diameter-of-binary-tree Diameter of Binary Tree (LeetCode 543) https://leettube.dev/posters/diameter-of-binary-tree.jpg Find the longest path between any two nodes. Each node asks its children for their heights, and the path bending through it is left plus right. https://leettube.dev/api/video/diameter-of-binary-tree.mp4 100 2026-10-05T21:56:08.127Z 2026-10-05T21:56:08.127Z monthly 0.8 https://leettube.dev/watch/balanced-binary-tree Balanced Binary Tree (LeetCode 110) https://leettube.dev/posters/balanced-binary-tree.jpg Is every node's left and right height within one? Return each subtree's height from the bottom up, and a -1 the moment any node is lopsided. https://leettube.dev/api/video/balanced-binary-tree.mp4 99 2026-10-06T09:38:02.648Z 2026-10-06T09:38:02.648Z monthly 0.8 https://leettube.dev/watch/subtree-of-another-tree Subtree of Another Tree (LeetCode 572) https://leettube.dev/posters/subtree-of-another-tree.jpg Check if one binary tree appears inside another. Try every node as a starting point and run a same-tree check from there. https://leettube.dev/api/video/subtree-of-another-tree.mp4 99 2026-10-06T02:19:06.596Z 2026-10-06T02:19:06.596Z monthly 0.8 https://leettube.dev/watch/level-order-traversal Level Order Traversal (LeetCode 102) https://leettube.dev/posters/level-order-traversal.jpg Read a binary tree one level at a time. Keep a queue, and each round empty exactly the nodes that were in it when the round began. https://leettube.dev/api/video/level-order-traversal.mp4 90 2026-10-05T21:56:12.020Z 2026-10-05T21:56:12.020Z monthly 0.8 https://leettube.dev/watch/binary-tree-right-side-view Binary Tree Right Side View (LeetCode 199) https://leettube.dev/posters/binary-tree-right-side-view.jpg List the nodes you'd see standing to the right of a binary tree. Walk it level by level and keep the last node on each level. https://leettube.dev/api/video/binary-tree-right-side-view.mp4 93 2026-10-06T02:16:50.080Z 2026-10-06T02:16:50.080Z monthly 0.8 https://leettube.dev/watch/validate-bst Validate BST (LeetCode 98) https://leettube.dev/posters/validate-bst.jpg Is this a valid binary search tree? Checking each parent and child isn't enough; pass down the lowest and highest values each subtree is allowed. https://leettube.dev/api/video/validate-bst.mp4 98 2026-10-05T21:56:21.638Z 2026-10-05T21:56:21.638Z monthly 0.8 https://leettube.dev/watch/convert-sorted-array-to-binary-search-tree Convert Sorted Array to Binary Search Tree (LeetCode 108) https://leettube.dev/posters/convert-sorted-array-to-binary-search-tree.jpg Turn a sorted array into a height-balanced BST. The middle value becomes the root, and each half recursively builds its own subtree. https://leettube.dev/api/video/convert-sorted-array-to-binary-search-tree.mp4 97 2026-10-06T10:28:43.756Z 2026-10-06T10:28:43.756Z monthly 0.8 https://leettube.dev/watch/kth-smallest-in-bst Kth Smallest Element in a BST (LeetCode 230) https://leettube.dev/posters/kth-smallest-in-bst.jpg Find the kth smallest value in a BST. An inorder walk visits values in sorted order, so stop at the kth node you reach. https://leettube.dev/api/video/kth-smallest-in-bst.mp4 98 2026-10-05T21:56:11.266Z 2026-10-05T21:56:11.266Z monthly 0.8 https://leettube.dev/watch/lowest-common-ancestor Lowest Common Ancestor (LeetCode 236) https://leettube.dev/posters/lowest-common-ancestor.jpg Find the deepest node above two targets in one pass: each node reports what it found, and the node where both sides answer wins. https://leettube.dev/api/video/lowest-common-ancestor.mp4 94 2026-10-05T21:56:13.121Z 2026-10-05T21:56:13.121Z monthly 0.8 https://leettube.dev/watch/construct-binary-tree-from-preorder-and-inorder Construct Binary Tree from Preorder and Inorder Traversal (LeetCode 105) https://leettube.dev/posters/construct-binary-tree-from-preorder-and-inorder.jpg Rebuild a tree from two traversals. Preorder names each root; its spot in inorder splits the left and right subtrees. https://leettube.dev/api/video/construct-binary-tree-from-preorder-and-inorder.mp4 107 2026-10-05T21:56:06.188Z 2026-10-05T21:56:06.188Z monthly 0.8 https://leettube.dev/watch/implement-trie Implement Trie (LeetCode 208) https://leettube.dev/posters/implement-trie.jpg Insert words, search them and check prefixes. A tree of letters lets words that share a prefix share a path. https://leettube.dev/api/video/implement-trie.mp4 93 2026-10-05T21:56:09.268Z 2026-10-05T21:56:09.268Z monthly 0.8 https://leettube.dev/watch/binary-tree-maximum-path-sum Binary Tree Maximum Path Sum (LeetCode 124) https://leettube.dev/posters/binary-tree-maximum-path-sum.jpg Find the best path anywhere in a tree. Each node reports its best one-sided branch upward and checks the path that bends through it. https://leettube.dev/api/video/binary-tree-maximum-path-sum.mp4 103 2026-10-05T21:56:04.630Z 2026-10-05T21:56:04.630Z monthly 0.8 https://leettube.dev/watch/binary-tree-cameras Binary Tree Cameras (LeetCode 968) https://leettube.dev/posters/binary-tree-cameras.jpg Fewest cameras to watch every node: work up from the leaves with three states, put a camera on any parent of an unwatched child. https://leettube.dev/api/video/binary-tree-cameras.mp4 97 2026-10-06T15:13:32.592Z 2026-10-06T15:13:32.592Z monthly 0.8 https://leettube.dev/watch/serialize-and-deserialize-binary-tree Serialize and Deserialize Binary Tree (LeetCode 297) https://leettube.dev/posters/serialize-and-deserialize-binary-tree.jpg Turn a binary tree into a string and back. Write it in preorder with a marker for every missing child, then read it back the same way. https://leettube.dev/api/video/serialize-and-deserialize-binary-tree.mp4 103 2026-10-06T04:04:36.166Z 2026-10-06T04:04:36.166Z monthly 0.8 https://leettube.dev/watch/intro-backtracking Backtracking tutorial https://leettube.dev/posters/intro-backtracking.jpg Build an answer one choice at a time and undo the ones that lead nowhere: choose, recurse, then un-choose so the next choice starts clean. https://leettube.dev/api/video/intro-backtracking.mp4 45 2026-10-05T21:56:09.439Z 2026-10-05T21:56:09.439Z monthly 0.8 https://leettube.dev/watch/subsets Subsets (LeetCode 78) https://leettube.dev/posters/subsets.jpg List every subset of a set of distinct numbers, empty one included. For each number, branch on taking it or leaving it. https://leettube.dev/api/video/subsets.mp4 97 2026-10-05T21:56:19.631Z 2026-10-05T21:56:19.631Z monthly 0.8 https://leettube.dev/watch/subsets-ii Subsets II (LeetCode 90) https://leettube.dev/posters/subsets-ii.jpg List every subset of a list that has duplicates, with no repeats. Sort first, then skip a value already tried at the same depth. https://leettube.dev/api/video/subsets-ii.mp4 100 2026-10-06T04:14:21.666Z 2026-10-06T04:14:21.666Z monthly 0.8 https://leettube.dev/watch/combinations Combinations (LeetCode 77) https://leettube.dev/posters/combinations.jpg Every way to choose k numbers from 1 to n. Pick the next number only from those after the last pick, recurse, then undo the pick and try the next. https://leettube.dev/api/video/combinations.mp4 102 2026-10-06T10:26:53.243Z 2026-10-06T10:26:53.243Z monthly 0.8 https://leettube.dev/watch/generate-parentheses Generate Parentheses (LeetCode 22) https://leettube.dev/posters/generate-parentheses.jpg List every balanced string of n pairs of parentheses. Add an opener while you have one left, and a closer only when it has a match. https://leettube.dev/api/video/generate-parentheses.mp4 99 2026-10-06T00:55:16.542Z 2026-10-06T00:55:16.542Z monthly 0.8 https://leettube.dev/watch/letter-combinations Letter Combinations (LeetCode 17) https://leettube.dev/posters/letter-combinations.jpg Spell every word a phone number could make. Fill one position at a time from its key, recurse for the rest, then pop and try the next letter. https://leettube.dev/api/video/letter-combinations.mp4 100 2026-10-05T21:56:12.014Z 2026-10-05T21:56:12.014Z monthly 0.8 https://leettube.dev/watch/permutations Permutations (LeetCode 46) https://leettube.dev/posters/permutations.jpg List every order of a set of numbers. Fill one seat at a time with a number you haven't used, recurse, then take it back and try the next. https://leettube.dev/api/video/permutations.mp4 96 2026-10-05T21:56:17.286Z 2026-10-05T21:56:17.286Z monthly 0.8 https://leettube.dev/watch/permutations-ii Permutations II (LeetCode 47) https://leettube.dev/posters/permutations-ii.jpg Every distinct ordering of numbers that may repeat. Sort first, then skip a copy whenever its twin to the left is still unused in this branch. https://leettube.dev/api/video/permutations-ii.mp4 104 2026-10-06T09:32:34.705Z 2026-10-06T09:32:34.705Z monthly 0.8 https://leettube.dev/watch/combination-sum Combination Sum (LeetCode 39) https://leettube.dev/posters/combination-sum.jpg Find every combination that adds up to the target, reusing numbers as often as you like. Recurse with a start index so each combination appears once. https://leettube.dev/api/video/combination-sum.mp4 102 2026-10-05T21:56:06.030Z 2026-10-05T21:56:06.030Z monthly 0.8 https://leettube.dev/watch/combination-sum-ii Combination Sum II (LeetCode 40) https://leettube.dev/posters/combination-sum-ii.jpg Find every combination that sums to a target, using each number once. Sort, skip repeats at the same depth, and stop once numbers get too big. https://leettube.dev/api/video/combination-sum-ii.mp4 112 2026-10-06T04:29:43.863Z 2026-10-06T04:29:43.863Z monthly 0.8 https://leettube.dev/watch/combination-sum-iii Combination Sum III (LeetCode 216) https://leettube.dev/posters/combination-sum-iii.jpg Every set of k distinct digits from 1 to 9 that sums to n: pick in increasing order, track what's left, and stop once a digit is too big. https://leettube.dev/api/video/combination-sum-iii.mp4 95 2026-10-06T12:16:08.668Z 2026-10-06T12:16:08.668Z monthly 0.8 https://leettube.dev/watch/partition-to-k-equal-sum-subsets Partition to K Equal Sum Subsets (LeetCode 698) https://leettube.dev/posters/partition-to-k-equal-sum-subsets.jpg Split numbers into k groups with equal sums: find the target, place the biggest numbers first, and skip buckets that repeat a sum. https://leettube.dev/api/video/partition-to-k-equal-sum-subsets.mp4 99 2026-10-06T15:19:06.187Z 2026-10-06T15:19:06.187Z monthly 0.8 https://leettube.dev/watch/palindrome-partitioning Palindrome Partitioning (LeetCode 131) https://leettube.dev/posters/palindrome-partitioning.jpg Split a string into palindromes every possible way. Cut off a palindrome prefix, recurse on the rest, then undo the cut and try a longer one. https://leettube.dev/api/video/palindrome-partitioning.mp4 105 2026-10-05T21:56:16.280Z 2026-10-05T21:56:16.280Z monthly 0.8 https://leettube.dev/watch/restore-ip-addresses Restore IP Addresses (LeetCode 93) https://leettube.dev/posters/restore-ip-addresses.jpg Split a digit string into four valid IP parts: try a 1, 2 or 3 digit chunk, recurse, and back up when a part tops 255 or has a leading zero. https://leettube.dev/api/video/restore-ip-addresses.mp4 101 2026-10-06T06:19:05.954Z 2026-10-06T06:19:05.954Z monthly 0.8 https://leettube.dev/watch/word-search Word Search (LeetCode 79) https://leettube.dev/posters/word-search.jpg Can you spell a word through neighbouring letters in a grid? Try each path, mark the cells you use, and unmark them when you back out. https://leettube.dev/api/video/word-search.mp4 103 2026-10-05T21:56:23.735Z 2026-10-05T21:56:23.735Z monthly 0.8 https://leettube.dev/watch/word-search-ii Word Search II (LeetCode 212) https://leettube.dev/posters/word-search-ii.jpg Find every word from a list on a letter grid. Build a trie of the words and walk the board once, following only paths the trie allows. https://leettube.dev/api/video/word-search-ii.mp4 98 2026-10-05T21:56:22.273Z 2026-10-05T21:56:22.273Z monthly 0.8 https://leettube.dev/watch/n-queens N-Queens (LeetCode 51) https://leettube.dev/posters/n-queens.jpg Place n queens so none can attack another. Go row by row, track the columns and both diagonals in use, and back up at dead ends. https://leettube.dev/api/video/n-queens.mp4 100 2026-10-05T21:56:15.118Z 2026-10-05T21:56:15.118Z monthly 0.8 https://leettube.dev/watch/n-queens-ii N-Queens II (LeetCode 52) https://leettube.dev/posters/n-queens-ii.jpg Count the ways to place n queens with no attacks: one queen per row, three sets for columns and diagonals, undo and try the next. https://leettube.dev/api/video/n-queens-ii.mp4 96 2026-10-06T14:32:39.648Z 2026-10-06T14:32:39.648Z monthly 0.8 https://leettube.dev/watch/sudoku-solver Sudoku Solver (LeetCode 37) https://leettube.dev/posters/sudoku-solver.jpg Fill a Sudoku grid so every row, column and box holds 1 to 9. Try a digit, keep going while it fits, and undo it when you hit a dead end. https://leettube.dev/api/video/sudoku-solver.mp4 101 2026-10-06T00:49:16.711Z 2026-10-06T00:49:16.711Z monthly 0.8 https://leettube.dev/watch/intro-dynamic-programming Dynamic programming tutorial https://leettube.dev/posters/intro-dynamic-programming.jpg Never solve the same problem twice. Save each answer as you recurse, or fill a table from the smallest case up. https://leettube.dev/api/video/intro-dynamic-programming.mp4 44 2026-10-05T21:56:10.190Z 2026-10-05T21:56:10.190Z monthly 0.8 https://leettube.dev/watch/climbing-stairs Climbing Stairs (LeetCode 70) https://leettube.dev/posters/climbing-stairs.jpg Count the ways up a staircase taking one or two steps at a time. Each stair's count is the sum of the two below it, so climb once and keep just two numbers. https://leettube.dev/api/video/climbing-stairs.mp4 85 2026-10-05T21:56:05.512Z 2026-10-05T21:56:05.512Z monthly 0.8 https://leettube.dev/watch/house-robber House Robber (LeetCode 198) https://leettube.dev/posters/house-robber.jpg Rob the most cash from a row of houses without hitting two neighbours. Carry the best haul so far, one house at a time. https://leettube.dev/api/video/house-robber.mp4 85 2026-10-05T21:56:08.847Z 2026-10-05T21:56:08.847Z monthly 0.8 https://leettube.dev/watch/house-robber-ii House Robber II (LeetCode 213) https://leettube.dev/posters/house-robber-ii.jpg Rob houses in a circle without hitting two neighbours. The first and last touch, so run House Robber twice: once without each end. https://leettube.dev/api/video/house-robber-ii.mp4 95 2026-10-06T04:20:46.505Z 2026-10-06T04:20:46.505Z monthly 0.8 https://leettube.dev/watch/maximum-product-subarray Maximum Product Subarray (LeetCode 152) https://leettube.dev/posters/maximum-product-subarray.jpg Largest product of a contiguous run: track the high and the low at each step, because a negative number swaps them. https://leettube.dev/api/video/maximum-product-subarray.mp4 101 2026-10-06T11:22:55.303Z 2026-10-06T11:22:55.303Z monthly 0.8 https://leettube.dev/watch/best-time-to-buy-and-sell-stock-with-cooldown Best Time to Buy and Sell Stock with Cooldown (LeetCode 309) https://leettube.dev/posters/best-time-to-buy-and-sell-stock-with-cooldown.jpg Max profit when every sale forces a one-day rest: track three states each day (holding, just sold, resting) and step them forward together. https://leettube.dev/api/video/best-time-to-buy-and-sell-stock-with-cooldown.mp4 102 2026-10-06T15:11:33.810Z 2026-10-06T15:11:33.810Z monthly 0.8 https://leettube.dev/watch/decode-ways Decode Ways (LeetCode 91) https://leettube.dev/posters/decode-ways.jpg Count the ways a string of digits can decode into letters. Each digit can stand alone or pair with the one before it, like climbing stairs. https://leettube.dev/api/video/decode-ways.mp4 100 2026-10-06T00:57:02.458Z 2026-10-06T00:57:02.458Z monthly 0.8 https://leettube.dev/watch/palindromic-substrings Palindromic Substrings (LeetCode 647) https://leettube.dev/posters/palindromic-substrings.jpg Count every palindrome hiding in a string. Pick each centre, letter or gap, and expand outward while both ends match, one count per step. https://leettube.dev/api/video/palindromic-substrings.mp4 110 2026-10-06T01:45:29.218Z 2026-10-06T01:45:29.218Z monthly 0.8 https://leettube.dev/watch/unique-paths Unique Paths (LeetCode 62) https://leettube.dev/posters/unique-paths.jpg Count a robot's routes across a grid moving only right or down. Each cell's count is the cell above plus the cell to the left. https://leettube.dev/api/video/unique-paths.mp4 97 2026-10-05T21:56:20.806Z 2026-10-05T21:56:20.806Z monthly 0.8 https://leettube.dev/watch/coin-change Coin Change (LeetCode 322) https://leettube.dev/posters/coin-change.jpg The fewest coins that add up to an amount. Greedy fails, so build up from zero, reusing the best answer for each smaller amount. https://leettube.dev/api/video/coin-change.mp4 97 2026-10-05T21:56:06.054Z 2026-10-05T21:56:06.054Z monthly 0.8 https://leettube.dev/watch/perfect-squares Perfect Squares (LeetCode 279) https://leettube.dev/posters/perfect-squares.jpg Fewest squares that sum to n: build a table up from zero, trying every square that fits. It's Coin Change with squares as coins. https://leettube.dev/api/video/perfect-squares.mp4 100 2026-10-06T11:17:16.065Z 2026-10-06T11:17:16.065Z monthly 0.8 https://leettube.dev/watch/partition-equal-subset-sum Partition Equal Subset Sum (LeetCode 416) https://leettube.dev/posters/partition-equal-subset-sum.jpg Split the numbers into two equal-sum halves. Track which sums up to half the total are reachable, adding one number at a time, right to left. https://leettube.dev/api/video/partition-equal-subset-sum.mp4 101 2026-10-05T21:56:16.777Z 2026-10-05T21:56:16.777Z monthly 0.8 https://leettube.dev/watch/word-break Word Break (LeetCode 139) https://leettube.dev/posters/word-break.jpg Can a string be split into dictionary words? Mark each position you can reach, building on earlier marks, until you reach the end. https://leettube.dev/api/video/word-break.mp4 97 2026-10-05T21:56:21.581Z 2026-10-05T21:56:21.581Z monthly 0.8 https://leettube.dev/watch/longest-increasing-subsequence Longest Increasing Subsequence (LeetCode 300) https://leettube.dev/posters/longest-increasing-subsequence.jpg Find the longest strictly rising run you can pick out of a list, skipping but never reordering. Build the answer for each ending number from the ones before it, then a bonus O(n log n) trick. https://leettube.dev/api/video/longest-increasing-subsequence.mp4 100 2026-10-05T21:56:12.881Z 2026-10-05T21:56:12.881Z monthly 0.8 https://leettube.dev/watch/longest-common-subsequence Longest Common Subsequence (LeetCode 1143) https://leettube.dev/posters/longest-common-subsequence.jpg Find the longest sequence two strings share in order. Fill a grid: matching letters extend the diagonal, otherwise take the better neighbour. https://leettube.dev/api/video/longest-common-subsequence.mp4 103 2026-10-05T21:56:12.898Z 2026-10-05T21:56:12.898Z monthly 0.8 https://leettube.dev/watch/distinct-subsequences Distinct Subsequences (LeetCode 115) https://leettube.dev/posters/distinct-subsequences.jpg Count the ways to pick letters of s, in order, that spell t: each letter is skipped or used, and a table adds up both choices. https://leettube.dev/api/video/distinct-subsequences.mp4 94 2026-10-06T11:24:49.031Z 2026-10-06T11:24:49.031Z monthly 0.8 https://leettube.dev/watch/edit-distance Edit Distance (LeetCode 72) https://leettube.dev/posters/edit-distance.jpg The fewest inserts, deletes and replaces to turn one word into another. Fill a table where each cell takes the cheapest of three neighbours. https://leettube.dev/api/video/edit-distance.mp4 98 2026-10-05T21:56:07.692Z 2026-10-05T21:56:07.692Z monthly 0.8 https://leettube.dev/watch/regular-expression-matching Regular Expression Matching (LeetCode 10) https://leettube.dev/posters/regular-expression-matching.jpg Match a string against a pattern with . and *. A grid of smaller answers decides each cell: a star can match zero copies or eat one more character. https://leettube.dev/api/video/regular-expression-matching.mp4 100 2026-10-06T05:26:56.917Z 2026-10-06T05:26:56.917Z monthly 0.8 https://leettube.dev/watch/longest-valid-parentheses Longest Valid Parentheses (LeetCode 32) https://leettube.dev/posters/longest-valid-parentheses.jpg Find the longest well-formed run of brackets. Each ) extends the valid run ending just before its matching (, so one pass of stored lengths works. https://leettube.dev/api/video/longest-valid-parentheses.mp4 95 2026-10-06T09:30:24.867Z 2026-10-06T09:30:24.867Z monthly 0.8 https://leettube.dev/watch/intro-graphs Graphs tutorial https://leettube.dev/posters/intro-graphs.jpg Nodes and edges: explore outward from a start with a queue (breadth first) or a stack (depth first), stamping each node so you never loop. https://leettube.dev/api/video/intro-graphs.mp4 47 2026-10-05T21:56:10.495Z 2026-10-05T21:56:10.495Z monthly 0.8 https://leettube.dev/watch/number-of-islands Number of Islands (LeetCode 200) https://leettube.dev/posters/number-of-islands.jpg Count the islands in a grid of land and water. Scan for land, and sink each island you find so it's only counted once. https://leettube.dev/api/video/number-of-islands.mp4 99 2026-10-05T21:56:16.303Z 2026-10-05T21:56:16.303Z monthly 0.8 https://leettube.dev/watch/number-of-provinces Number of Provinces (LeetCode 547) https://leettube.dev/posters/number-of-provinces.jpg Count groups of connected cities: pick an unvisited city, flood its whole province with a search, and count how many floods it takes. https://leettube.dev/api/video/number-of-provinces.mp4 94 2026-10-06T14:34:30.620Z 2026-10-06T14:34:30.620Z monthly 0.8 https://leettube.dev/watch/rotting-oranges Rotting Oranges (LeetCode 994) https://leettube.dev/posters/rotting-oranges.jpg How many minutes until every orange rots? Start a breadth-first search from all the rotten ones at once, one ring per minute. https://leettube.dev/api/video/rotting-oranges.mp4 100 2026-10-05T21:56:18.940Z 2026-10-05T21:56:18.940Z monthly 0.8 https://leettube.dev/watch/pacific-atlantic-water-flow Pacific Atlantic Water Flow (LeetCode 417) https://leettube.dev/posters/pacific-atlantic-water-flow.jpg Which cells drain to both oceans? Flip the flow: flood uphill from each coastline, then keep the cells both tides reach. https://leettube.dev/api/video/pacific-atlantic-water-flow.mp4 93 2026-10-05T21:56:16.249Z 2026-10-05T21:56:16.249Z monthly 0.8 https://leettube.dev/watch/surrounded-regions Surrounded Regions (LeetCode 130) https://leettube.dev/posters/surrounded-regions.jpg Capture every region of O cells walled in by X. Flood fill from the border to mark the O cells that escape; the rest get captured. https://leettube.dev/api/video/surrounded-regions.mp4 96 2026-10-06T01:16:23.195Z 2026-10-06T01:16:23.195Z monthly 0.8 https://leettube.dev/watch/longest-increasing-path-in-a-matrix Longest Increasing Path in a Matrix (LeetCode 329) https://leettube.dev/posters/longest-increasing-path-in-a-matrix.jpg Find the longest strictly rising path in a grid. Depth-first search from each cell, and remember every answer so no cell is ever solved twice. https://leettube.dev/api/video/longest-increasing-path-in-a-matrix.mp4 106 2026-10-06T06:26:47.823Z 2026-10-06T06:26:47.823Z monthly 0.8 https://leettube.dev/watch/clone-graph Clone Graph (LeetCode 133) https://leettube.dev/posters/clone-graph.jpg Deep-copy a whole graph from one node. Walk it with depth-first search, and keep a map from each original to its copy so cycles are cloned once. https://leettube.dev/api/video/clone-graph.mp4 94 2026-10-05T21:56:05.675Z 2026-10-05T21:56:05.675Z monthly 0.8 https://leettube.dev/watch/course-schedule Course Schedule (LeetCode 207) https://leettube.dev/posters/course-schedule.jpg Decide whether you can finish every course given its prerequisites. Take courses with no locks left, and see if every course gets taken. https://leettube.dev/api/video/course-schedule.mp4 104 2026-10-05T21:56:06.827Z 2026-10-05T21:56:06.827Z monthly 0.8 https://leettube.dev/watch/course-schedule-ii Course Schedule II (LeetCode 210) https://leettube.dev/posters/course-schedule-ii.jpg Return a valid order to take every course. Count each course's prerequisites, start with the ones at zero, and unlock the rest as you go. https://leettube.dev/api/video/course-schedule-ii.mp4 102 2026-10-06T09:07:12.819Z 2026-10-06T09:07:12.819Z monthly 0.8 https://leettube.dev/watch/network-delay-time Network Delay Time (LeetCode 743) https://leettube.dev/posters/network-delay-time.jpg How long until a signal reaches every tower? Dijkstra's algorithm settles the earliest arrival first, using a min-heap. https://leettube.dev/api/video/network-delay-time.mp4 96 2026-10-05T21:56:15.480Z 2026-10-05T21:56:15.480Z monthly 0.8 https://leettube.dev/watch/cheapest-flights-within-k-stops Cheapest Flights Within K Stops (LeetCode 787) https://leettube.dev/posters/cheapest-flights-within-k-stops.jpg Find the cheapest fare with at most k stops. Relax every flight once per allowed hop, Bellman-Ford style, keeping last round's prices. https://leettube.dev/api/video/cheapest-flights-within-k-stops.mp4 106 2026-10-05T21:56:05.411Z 2026-10-05T21:56:05.411Z monthly 0.8 https://leettube.dev/watch/swim-in-rising-water Swim in Rising Water (LeetCode 778) https://leettube.dev/posters/swim-in-rising-water.jpg Water rises one unit a minute; when can you swim from corner to corner? Dijkstra with a min-heap keyed on the tallest cell along the path. https://leettube.dev/api/video/swim-in-rising-water.mp4 92 2026-10-06T10:30:27.757Z 2026-10-06T10:30:27.757Z monthly 0.8 https://leettube.dev/watch/reconstruct-itinerary Reconstruct Itinerary (LeetCode 332) https://leettube.dev/posters/reconstruct-itinerary.jpg Use every plane ticket once, starting at JFK, in alphabetical order. Depth-first search, then add each airport once its tickets run out. https://leettube.dev/api/video/reconstruct-itinerary.mp4 108 2026-10-06T01:22:19.686Z 2026-10-06T01:22:19.686Z monthly 0.8 https://leettube.dev/watch/redundant-connection Redundant Connection (LeetCode 684) https://leettube.dev/posters/redundant-connection.jpg A tree got one extra edge that closes a loop. Join nodes with union-find; the first edge whose ends already share a root is the extra one. https://leettube.dev/api/video/redundant-connection.mp4 100 2026-10-05T21:56:17.548Z 2026-10-05T21:56:17.548Z monthly 0.8 https://leettube.dev/watch/critical-connections-in-a-network Critical Connections in a Network (LeetCode 1192) https://leettube.dev/posters/critical-connections-in-a-network.jpg Find every link whose loss splits a network: one DFS stamps discovery times, carries low links up, and cuts where a child can't reach back. https://leettube.dev/api/video/critical-connections-in-a-network.mp4 94 2026-10-06T12:25:25.475Z 2026-10-06T12:25:25.475Z monthly 0.8 https://leettube.dev/watch/min-cost-to-connect-all-points Min Cost to Connect All Points (LeetCode 1584) https://leettube.dev/posters/min-cost-to-connect-all-points.jpg Join every point with the least total Manhattan distance. Grow a minimum spanning tree with Prim's algorithm, cheapest link first. https://leettube.dev/api/video/min-cost-to-connect-all-points.mp4 95 2026-10-06T04:02:19.815Z 2026-10-06T04:02:19.815Z monthly 0.8 https://leettube.dev/watch/word-ladder Word Ladder (LeetCode 127) https://leettube.dev/posters/word-ladder.jpg Change one letter at a time to reach the end word. Treat words as a graph and search breadth first, so the first hit is the shortest. https://leettube.dev/api/video/word-ladder.mp4 109 2026-10-05T21:56:22.413Z 2026-10-05T21:56:22.413Z monthly 0.8 https://leettube.dev/watch/intro-greedy Greedy tutorial https://leettube.dev/posters/intro-greedy.jpg Take what looks best right now and never go back. It works only when today's best pick can't hurt you later, so learn to spot when it's safe. https://leettube.dev/api/video/intro-greedy.mp4 46 2026-10-05T21:56:10.275Z 2026-10-05T21:56:10.275Z monthly 0.8 https://leettube.dev/watch/can-place-flowers Can Place Flowers (LeetCode 605) https://leettube.dev/posters/can-place-flowers.jpg Plant a flower wherever both neighbours are empty, scanning left to right. Planting early never hurts, so stop as soon as n fit. https://leettube.dev/api/video/can-place-flowers.mp4 95 2026-10-06T11:19:14.005Z 2026-10-06T11:19:14.005Z monthly 0.8 https://leettube.dev/watch/jump-game Jump Game (LeetCode 55) https://leettube.dev/posters/jump-game.jpg Can you hop from the first index to the last? Walk once, keeping the farthest spot you can reach; if you ever stand past it, you're stuck. https://leettube.dev/api/video/jump-game.mp4 95 2026-10-05T21:56:11.461Z 2026-10-05T21:56:11.461Z monthly 0.8 https://leettube.dev/watch/jump-game-ii Jump Game II (LeetCode 45) https://leettube.dev/posters/jump-game-ii.jpg Now count the fewest hops to the end. Treat each jump as a window of reachable spots, and only jump when you walk off its edge. https://leettube.dev/api/video/jump-game-ii.mp4 97 2026-10-05T21:56:11.616Z 2026-10-05T21:56:11.616Z monthly 0.8 https://leettube.dev/watch/gas-station Gas Station (LeetCode 134) https://leettube.dev/posters/gas-station.jpg Find the station where you can drive the whole loop. If the total gas covers the total cost, an answer exists; whenever the tank goes negative, start again from the next station. https://leettube.dev/api/video/gas-station.mp4 104 2026-10-05T21:56:08.456Z 2026-10-05T21:56:08.456Z monthly 0.8 https://leettube.dev/watch/minimum-domino-rotations-for-equal-row Minimum Domino Rotations For Equal Row (LeetCode 1007) https://leettube.dev/posters/minimum-domino-rotations-for-equal-row.jpg Fewest flips to make a domino row match: only the first domino's two values can work, so try each and keep the cheaper side. https://leettube.dev/api/video/minimum-domino-rotations-for-equal-row.mp4 98 2026-10-06T14:30:55.631Z 2026-10-06T14:30:55.631Z monthly 0.8 https://leettube.dev/watch/candy Candy (LeetCode 135) https://leettube.dev/posters/candy.jpg Hand out the fewest candies so higher-rated kids beat their neighbours. Sweep left to right, then right to left, keeping the larger count. https://leettube.dev/api/video/candy.mp4 101 2026-10-06T04:24:31.086Z 2026-10-06T04:24:31.086Z monthly 0.8 https://leettube.dev/watch/non-overlapping-intervals Non-overlapping Intervals (LeetCode 435) https://leettube.dev/posters/non-overlapping-intervals.jpg Remove the fewest intervals so the rest don't overlap. Sort by end time and keep whatever finishes first; every clash after that gets cut. https://leettube.dev/api/video/non-overlapping-intervals.mp4 98 2026-10-05T21:56:15.496Z 2026-10-05T21:56:15.496Z monthly 0.8 https://leettube.dev/watch/minimum-number-of-arrows-to-burst-balloons Minimum Number of Arrows to Burst Balloons (LeetCode 452) https://leettube.dev/posters/minimum-number-of-arrows-to-burst-balloons.jpg Sort balloons by where they end and shoot each arrow at the earliest end. It pops every balloon still overlapping it, so you need the fewest. https://leettube.dev/api/video/minimum-number-of-arrows-to-burst-balloons.mp4 97 2026-10-06T06:28:53.896Z 2026-10-06T06:28:53.896Z monthly 0.8 https://leettube.dev/watch/partition-labels Partition Labels (LeetCode 763) https://leettube.dev/posters/partition-labels.jpg Cut a string into as many pieces as possible with no letter in two pieces. Track where each letter last appears, and cut when you reach it. https://leettube.dev/api/video/partition-labels.mp4 92 2026-10-05T21:56:16.810Z 2026-10-05T21:56:16.810Z monthly 0.8 https://leettube.dev/watch/boats-to-save-people Boats to Save People (LeetCode 881) https://leettube.dev/posters/boats-to-save-people.jpg Each boat holds two people under a weight limit. Sort, then pair the heaviest with the lightest when they fit; otherwise the heaviest rides alone. https://leettube.dev/api/video/boats-to-save-people.mp4 103 2026-10-06T09:15:10.809Z 2026-10-06T09:15:10.809Z monthly 0.8 https://leettube.dev/watch/remove-k-digits Remove K Digits (LeetCode 402) https://leettube.dev/posters/remove-k-digits.jpg Delete k digits to make the smallest number. Keep a rising stack and pop any bigger digit before a smaller one while deletions remain. https://leettube.dev/api/video/remove-k-digits.mp4 101 2026-10-06T09:34:21.358Z 2026-10-06T09:34:21.358Z monthly 0.8 https://leettube.dev/watch/two-city-scheduling Two City Scheduling (LeetCode 1029) https://leettube.dev/posters/two-city-scheduling.jpg Send 2n people to two cities at least cost: book everyone to B, sort by A minus B, and switch the cheapest half to A. https://leettube.dev/api/video/two-city-scheduling.mp4 96 2026-10-06T11:21:01.755Z 2026-10-06T11:21:01.755Z monthly 0.8 https://leettube.dev/watch/valid-parenthesis-string Valid Parenthesis String (LeetCode 678) https://leettube.dev/posters/valid-parenthesis-string.jpg Check brackets where each star can be open, close or nothing. Track the lowest and highest possible open count instead of choosing. https://leettube.dev/api/video/valid-parenthesis-string.mp4 103 2026-10-06T02:23:17.118Z 2026-10-06T02:23:17.118Z monthly 0.8 https://leettube.dev/watch/maximum-subarray Maximum Subarray (LeetCode 53) https://leettube.dev/posters/maximum-subarray.jpg Find the stretch of numbers with the biggest sum in one pass: carry a running total, and drop it the moment it goes negative. https://leettube.dev/api/video/maximum-subarray.mp4 105 2026-10-05T21:56:13.790Z 2026-10-05T21:56:13.790Z monthly 0.8 https://leettube.dev/watch/hand-of-straights Hand of Straights (LeetCode 846) https://leettube.dev/posters/hand-of-straights.jpg Split a hand of cards into runs of consecutive values. Always start a run at the smallest card left, since nothing else can come before it. https://leettube.dev/api/video/hand-of-straights.mp4 104 2026-10-05T21:56:08.761Z 2026-10-05T21:56:08.761Z monthly 0.8 https://leettube.dev/watch/task-scheduler Task Scheduler (LeetCode 621) https://leettube.dev/posters/task-scheduler.jpg Find the fewest slots to run every task with n idle gaps between repeats. The most frequent task sets a frame; the rest fill its gaps. https://leettube.dev/api/video/task-scheduler.mp4 104 2026-10-05T21:56:19.639Z 2026-10-05T21:56:19.639Z monthly 0.8 https://leettube.dev/watch/merge-triplets-to-form-target-triplet Merge Triplets to Form Target Triplet (LeetCode 1899) https://leettube.dev/posters/merge-triplets-to-form-target-triplet.jpg Can some triplets merge, by taking maxes, into a target? Skip any triplet that overshoots, then check the safe ones still reach every value. https://leettube.dev/api/video/merge-triplets-to-form-target-triplet.mp4 96 2026-10-06T00:51:14.601Z 2026-10-06T00:51:14.601Z monthly 0.8 https://leettube.dev/watch/intro-bits-and-math Bits and math tutorial https://leettube.dev/posters/intro-bits-and-math.jpg Every number is a row of lamps, on or off. AND, OR and XOR flip them all at once, and x XOR x is zero, so pairs cancel. https://leettube.dev/api/video/intro-bits-and-math.mp4 46 2026-10-05T21:56:09.858Z 2026-10-05T21:56:09.858Z monthly 0.8 https://leettube.dev/watch/single-number Single Number (LeetCode 136) https://leettube.dev/posters/single-number.jpg Every number appears twice except one. XOR them all together: pairs cancel to zero, and the loner is all that's left. https://leettube.dev/api/video/single-number.mp4 98 2026-10-05T21:56:18.688Z 2026-10-05T21:56:18.688Z monthly 0.8 https://leettube.dev/watch/number-of-1-bits Number of 1 Bits (LeetCode 191) https://leettube.dev/posters/number-of-1-bits.jpg Count the ones in a number's binary form. n & (n - 1) clears the lowest one bit, so count how many times you can do it before reaching zero. https://leettube.dev/api/video/number-of-1-bits.mp4 102 2026-10-05T21:56:15.837Z 2026-10-05T21:56:15.837Z monthly 0.8 https://leettube.dev/watch/hamming-distance Hamming Distance (LeetCode 461) https://leettube.dev/posters/hamming-distance.jpg Count the bit positions where two numbers differ: XOR marks every difference, then clear the lowest set bit until none are left. https://leettube.dev/api/video/hamming-distance.mp4 101 2026-10-06T12:23:39.381Z 2026-10-06T12:23:39.381Z monthly 0.8 https://leettube.dev/watch/counting-bits Counting Bits (LeetCode 338) https://leettube.dev/posters/counting-bits.jpg Count the ones in every number from 0 to n. Each answer is the count for i shifted right one bit, plus its last bit. https://leettube.dev/api/video/counting-bits.mp4 97 2026-10-05T21:56:06.778Z 2026-10-05T21:56:06.778Z monthly 0.8 https://leettube.dev/watch/rotate-image Rotate Image (LeetCode 48) https://leettube.dev/posters/rotate-image.jpg Spin a square grid a quarter turn without a second grid: flip it across the diagonal, then mirror each row. https://leettube.dev/api/video/rotate-image.mp4 97 2026-10-05T21:56:18.965Z 2026-10-05T21:56:18.965Z monthly 0.8 https://leettube.dev/watch/spiral-matrix Spiral Matrix (LeetCode 54) https://leettube.dev/posters/spiral-matrix.jpg Read a grid in spiral order by walking four walls: across the top, down the right, back along the bottom, up the left, then shrink inward. https://leettube.dev/api/video/spiral-matrix.mp4 100 2026-10-06T06:24:42.811Z 2026-10-06T06:24:42.811Z monthly 0.8 https://leettube.dev/watch/missing-number Missing Number (LeetCode 268) https://leettube.dev/posters/missing-number.jpg One number from 0 to n is gone. Add up what 0 to n should total, subtract what you have, and the gap is the answer. https://leettube.dev/api/video/missing-number.mp4 103 2026-10-05T21:56:14.857Z 2026-10-05T21:56:14.857Z monthly 0.8 https://leettube.dev/watch/pow-x-n Pow(x, n) (LeetCode 50) https://leettube.dev/posters/pow-x-n.jpg Raise x to the power n in about log n steps: square the base and halve the exponent, setting aside one copy whenever it's odd. https://leettube.dev/api/video/pow-x-n.mp4 100 2026-10-05T21:56:16.988Z 2026-10-05T21:56:16.988Z monthly 0.8 https://leettube.dev/watch/sqrtx Sqrt(x) (LeetCode 69) https://leettube.dev/posters/sqrtx.jpg Integer square root with no built-ins: binary search the answer, square the middle, and keep the largest value whose square still fits. https://leettube.dev/api/video/sqrtx.mp4 103 2026-10-06T15:17:18.326Z 2026-10-06T15:17:18.326Z monthly 0.8 https://leettube.dev/watch/reverse-bits Reverse Bits (LeetCode 190) https://leettube.dev/posters/reverse-bits.jpg Flip the order of the 32 bits in a number. Peel the last bit off the input and push it onto the result, 32 times, with shifts. https://leettube.dev/api/video/reverse-bits.mp4 96 2026-10-05T21:56:17.934Z 2026-10-05T21:56:17.934Z monthly 0.8 https://leettube.dev/watch/sum-of-two-integers Sum of Two Integers (LeetCode 371) https://leettube.dev/posters/sum-of-two-integers.jpg Add two numbers without plus or minus. XOR adds each column, AND shifted left is the carry, and you repeat until the carry is zero. https://leettube.dev/api/video/sum-of-two-integers.mp4 105 2026-10-05T21:56:20.042Z 2026-10-05T21:56:20.042Z monthly 0.8 https://leettube.dev/watch/reverse-integer Reverse Integer (LeetCode 7) https://leettube.dev/posters/reverse-integer.jpg Reverse the digits of a 32-bit integer. Pop the last digit, push it onto the result, and check for overflow before each push. https://leettube.dev/api/video/reverse-integer.mp4 107 2026-10-05T21:56:18.585Z 2026-10-05T21:56:18.585Z monthly 0.8 https://leettube.dev/watch/palindrome-number Palindrome Number (LeetCode 9) https://leettube.dev/posters/palindrome-number.jpg Is an integer a palindrome without turning it into a string? Peel digits off the end to rebuild the back half, and stop once it meets the front. https://leettube.dev/api/video/palindrome-number.mp4 102 2026-10-06T10:25:07.520Z 2026-10-06T10:25:07.520Z monthly 0.8 https://leettube.dev/watch/happy-number Happy Number (LeetCode 202) https://leettube.dev/posters/happy-number.jpg Keep replacing a number with the sum of its digits squared. Either it reaches one or loops, and slow and fast pointers spot the loop. https://leettube.dev/api/video/happy-number.mp4 107 2026-10-06T04:06:59.779Z 2026-10-06T04:06:59.779Z monthly 0.8 https://leettube.dev/watch/plus-one Plus One (LeetCode 66) https://leettube.dev/posters/plus-one.jpg Add one to a number stored as an array of digits. Start from the right, turn each 9 into 0 and carry, and grow the array if needed. https://leettube.dev/api/video/plus-one.mp4 96 2026-10-06T04:16:24.338Z 2026-10-06T04:16:24.338Z monthly 0.8 https://leettube.dev/watch/multiply-strings Multiply Strings (LeetCode 43) https://leettube.dev/posters/multiply-strings.jpg Multiply two huge numbers stored as strings, like on paper: each digit pair lands at position i + j + 1, then carry the overflow leftward. https://leettube.dev/api/video/multiply-strings.mp4 108 2026-10-06T09:09:21.779Z 2026-10-06T09:09:21.779Z monthly 0.8 https://leettube.dev/watch/bitwise-and-of-numbers-range Bitwise AND of Numbers Range (LeetCode 201) https://leettube.dev/posters/bitwise-and-of-numbers-range.jpg AND together every number from left to right. Only the shared leading bits survive, so shift both ends right until they match. https://leettube.dev/api/video/bitwise-and-of-numbers-range.mp4 99 2026-10-06T01:20:08.428Z 2026-10-06T01:20:08.428Z monthly 0.8 https://leettube.dev/watch/intro-design Design tutorial https://leettube.dev/posters/intro-design.jpg Design problems hand you a blueprint with promised costs. Keep a little extra next to the data, like a map or a second value, so every method runs in constant time. https://leettube.dev/api/video/intro-design.mp4 44 2026-10-05T21:56:09.945Z 2026-10-05T21:56:09.945Z monthly 0.8 https://leettube.dev/watch/design-hashmap Design HashMap (LeetCode 706) https://leettube.dev/posters/design-hashmap.jpg Build a hash map with no built-in one: hash each key to a bucket, keep a short list there, and update or remove in place. https://leettube.dev/api/video/design-hashmap.mp4 98 2026-10-06T12:19:13.658Z 2026-10-06T12:19:13.658Z monthly 0.8 https://leettube.dev/watch/min-stack Min Stack (LeetCode 155) https://leettube.dev/posters/min-stack.jpg A stack that also reports its smallest value in constant time. Store each push next to the minimum at that moment, so popping brings the old minimum back. https://leettube.dev/api/video/min-stack.mp4 86 2026-10-05T21:56:14.543Z 2026-10-05T21:56:14.543Z monthly 0.8 https://leettube.dev/watch/implement-queue-using-stacks Implement Queue using Stacks (LeetCode 232) https://leettube.dev/posters/implement-queue-using-stacks.jpg Build a first-in, first-out queue from two stacks: push onto one, and pour it into the other only when that runs dry. Each item moves once. https://leettube.dev/api/video/implement-queue-using-stacks.mp4 102 2026-10-06T06:21:04.615Z 2026-10-06T06:21:04.615Z monthly 0.8 https://leettube.dev/watch/design-circular-queue Design Circular Queue (LeetCode 622) https://leettube.dev/posters/design-circular-queue.jpg Build a fixed-size ring queue: keep a head index and a count, wrap every step with modulo, and each operation is constant time. https://leettube.dev/api/video/design-circular-queue.mp4 100 2026-10-06T14:36:48.870Z 2026-10-06T14:36:48.870Z monthly 0.8 https://leettube.dev/watch/binary-search-tree-iterator Binary Search Tree Iterator (LeetCode 173) https://leettube.dev/posters/binary-search-tree-iterator.jpg Walk a BST in sorted order one call at a time. Keep a stack of the left spine; each next() pops a node and pushes its right child's left spine. https://leettube.dev/api/video/binary-search-tree-iterator.mp4 102 2026-10-06T10:23:09.629Z 2026-10-06T10:23:09.629Z monthly 0.8 https://leettube.dev/watch/lru-cache LRU Cache (LeetCode 146) https://leettube.dev/posters/lru-cache.jpg A fixed-size cache with constant-time get and put that evicts the least recently used key. A hash map finds the node, and a linked list keeps the order. https://leettube.dev/api/video/lru-cache.mp4 94 2026-10-05T21:56:13.713Z 2026-10-05T21:56:13.713Z monthly 0.8 https://leettube.dev/watch/lfu-cache LFU Cache (LeetCode 460) https://leettube.dev/posters/lfu-cache.jpg A cache that evicts the least frequently used key in O(1): a map from key to node, plus one list per use count and a pointer to the lowest count. https://leettube.dev/api/video/lfu-cache.mp4 100 2026-10-06T09:13:12.228Z 2026-10-06T09:13:12.228Z monthly 0.8 https://leettube.dev/watch/insert-delete-getrandom Insert Delete GetRandom O(1) (LeetCode 380) https://leettube.dev/posters/insert-delete-getrandom.jpg A set with constant-time insert, remove and random pick. Keep values in a list and their positions in a map, and delete by swapping with the last. https://leettube.dev/api/video/insert-delete-getrandom.mp4 91 2026-10-05T21:56:09.791Z 2026-10-05T21:56:09.791Z monthly 0.8 https://leettube.dev/watch/design-add-and-search-words Add and Search Words (LeetCode 211) https://leettube.dev/posters/design-add-and-search-words.jpg Store words in a trie and search patterns where a dot matches any letter, branching into every child only when you meet a dot. https://leettube.dev/api/video/design-add-and-search-words.mp4 99 2026-10-05T21:56:07.710Z 2026-10-05T21:56:07.710Z monthly 0.8 https://leettube.dev/watch/find-median-from-data-stream Find Median from Data Stream (LeetCode 295) https://leettube.dev/posters/find-median-from-data-stream.jpg Keep the running median as numbers stream in. Split them across two heaps, a max-heap for the low half and a min-heap for the high half. https://leettube.dev/api/video/find-median-from-data-stream.mp4 96 2026-10-05T21:56:08.111Z 2026-10-05T21:56:08.111Z monthly 0.8 https://leettube.dev/watch/time-based-key-value-store Time Based Key-Value Store (LeetCode 981) https://leettube.dev/posters/time-based-key-value-store.jpg Store values per key with timestamps, then fetch the latest value at or before a time. Times arrive sorted, so binary search them. https://leettube.dev/api/video/time-based-key-value-store.mp4 99 2026-10-05T21:56:20.189Z 2026-10-05T21:56:20.189Z monthly 0.8 https://leettube.dev/watch/merge-k-sorted-lists Merge k Sorted Lists (LeetCode 23) https://leettube.dev/posters/merge-k-sorted-lists.jpg Merge k sorted linked lists into one. The next node is always one of the k heads, so keep them in a min-heap and pop the smallest. https://leettube.dev/api/video/merge-k-sorted-lists.mp4 102 2026-10-05T21:56:14.220Z 2026-10-05T21:56:14.220Z monthly 0.8 https://leettube.dev/watch/design-twitter Design Twitter (LeetCode 355) https://leettube.dev/posters/design-twitter.jpg Build a tiny Twitter with post, follow and a news feed. Hash maps hold tweets and follows, and a max-heap merges the ten newest. https://leettube.dev/api/video/design-twitter.mp4 105 2026-10-05T21:56:07.447Z 2026-10-05T21:56:07.447Z monthly 0.8 https://leettube.dev/watch/kth-largest-element-in-a-stream Kth Largest Element in a Stream (LeetCode 703) https://leettube.dev/posters/kth-largest-element-in-a-stream.jpg Track the kth largest number as new ones stream in. Keep only the top k in a min-heap, and its smallest member is always the answer. https://leettube.dev/api/video/kth-largest-element-in-a-stream.mp4 88 2026-10-06T00:31:05.663Z 2026-10-06T00:31:05.663Z monthly 0.8 https://leettube.dev/watch/last-stone-weight Last Stone Weight (LeetCode 1046) https://leettube.dev/posters/last-stone-weight.jpg Smash the two heaviest stones together until at most one is left. A max-heap hands you the two biggest every turn in log time. https://leettube.dev/api/video/last-stone-weight.mp4 101 2026-10-06T01:52:35.079Z 2026-10-06T01:52:35.079Z monthly 0.8 https://leettube.dev/watch/detect-squares Detect Squares (LeetCode 2013) https://leettube.dev/posters/detect-squares.jpg Count the axis-aligned squares a query point makes with stored points. Keep point counts in a hash map and scan for diagonal corners. https://leettube.dev/api/video/detect-squares.mp4 97 2026-10-06T04:00:04.002Z 2026-10-06T04:00:04.002Z monthly 0.8 https://leettube.dev/watch/k-closest-points-to-origin K Closest Points to Origin (LeetCode 973) https://leettube.dev/posters/k-closest-points-to-origin.jpg Find the k points nearest the origin. Keep a max-heap of k seats and bump whoever sits farthest, so the k closest are left at the end. https://leettube.dev/api/video/k-closest-points-to-origin.mp4 100 2026-10-06T01:14:26.611Z 2026-10-06T01:14:26.611Z monthly 0.8