https://leettube.dev 2026-10-05T04:26:14.000Z weekly 1 https://leettube.dev/about monthly 0.5 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 2026-10-05T02:57:30.000Z 2026-10-05T02:57:30.000Z 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 2026-10-04T23:30:20.000Z 2026-10-04T23:30:20.000Z 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 2026-10-05T02:37:13.000Z 2026-10-05T02:37:13.000Z 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 2026-10-05T02:37:07.000Z 2026-10-05T02:37:07.000Z 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 2026-10-05T02:37:10.000Z 2026-10-05T02:37:10.000Z 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 2026-10-05T02:57:30.000Z 2026-10-05T02:57:30.000Z 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 2026-10-05T02:37:06.000Z 2026-10-05T02:37:06.000Z 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 2026-10-05T02:37:11.000Z 2026-10-05T02:37:11.000Z 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 2026-10-05T02:37:13.000Z 2026-10-05T02:37:13.000Z 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 2026-10-04T23:34:55.000Z 2026-10-04T23:34:55.000Z 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 2026-10-04T23:34:55.000Z 2026-10-04T23:34:55.000Z 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 2026-10-05T03:02:03.000Z 2026-10-05T03:02:03.000Z 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 2026-10-05T02:37:13.000Z 2026-10-05T02:37:13.000Z 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 2026-10-05T02:37:10.000Z 2026-10-05T02:37:10.000Z 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 2026-10-05T02:57:30.000Z 2026-10-05T02:57:30.000Z 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 2026-10-05T02:37:09.000Z 2026-10-05T02:37:09.000Z 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 2026-10-04T23:44:05.000Z 2026-10-04T23:44:05.000Z 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 2026-10-04T23:44:06.000Z 2026-10-04T23:44:06.000Z 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 2026-10-04T23:44:06.000Z 2026-10-04T23:44:06.000Z 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 2026-10-05T02:37:09.000Z 2026-10-05T02:37:09.000Z 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 2026-10-05T02:57:31.000Z 2026-10-05T02:57:31.000Z 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 2026-10-05T02:37:12.000Z 2026-10-05T02:37:12.000Z 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 2026-10-05T02:57:29.000Z 2026-10-05T02:57:29.000Z 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 2026-10-05T03:02:02.000Z 2026-10-05T03:02:02.000Z 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 2026-10-05T04:16:56.000Z 2026-10-05T04:16:56.000Z 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 2026-10-05T02:57:31.000Z 2026-10-05T02:57:31.000Z 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 2026-10-04T23:44:05.000Z 2026-10-04T23:44:05.000Z 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 2026-10-05T02:37:09.000Z 2026-10-05T02:37:09.000Z 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 2026-10-05T02:37:07.000Z 2026-10-05T02:37:07.000Z 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 2026-10-05T02:57:29.000Z 2026-10-05T02:57:29.000Z 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 2026-10-05T02:37:08.000Z 2026-10-05T02:37:08.000Z 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 2026-10-05T02:57:31.000Z 2026-10-05T02:57:31.000Z 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 2026-10-05T02:37:12.000Z 2026-10-05T02:37:12.000Z 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 2026-10-05T04:26:13.000Z 2026-10-05T04:26:13.000Z 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 2026-10-05T02:37:08.000Z 2026-10-05T02:37:08.000Z 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 2026-10-05T02:37:11.000Z 2026-10-05T02:37:11.000Z 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 2026-10-05T03:02:03.000Z 2026-10-05T03:02:03.000Z 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 2026-10-05T03:02:02.000Z 2026-10-05T03:02:02.000Z 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 2026-10-05T04:16:55.000Z 2026-10-05T04:16:55.000Z 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 2026-10-05T03:10:08.000Z 2026-10-05T03:10:08.000Z 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 2026-10-05T03:10:08.000Z 2026-10-05T03:10:08.000Z 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 2026-10-05T03:10:10.000Z 2026-10-05T03:10:10.000Z 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 2026-10-05T03:10:09.000Z 2026-10-05T03:10:09.000Z 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 2026-10-05T03:10:09.000Z 2026-10-05T03:10:09.000Z 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 2026-10-05T03:14:13.000Z 2026-10-05T03:14:13.000Z 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 2026-10-05T04:13:17.000Z 2026-10-05T04:13:17.000Z 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 2026-10-05T02:57:32.000Z 2026-10-05T02:57:32.000Z 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 2026-10-05T02:57:29.000Z 2026-10-05T02:57:29.000Z 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 2026-10-05T02:37:11.000Z 2026-10-05T02:37:11.000Z 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 2026-10-05T04:26:14.000Z 2026-10-05T04:26:14.000Z monthly 0.8