https://yosgi.github.io/en/tags/leetcode/Recent content in LeetCode on YosgiHugoenThu, 08 Oct 2026 01:31:25 +0000https://yosgi.github.io/en/post/1104-binary-tree-pathfinding/Thu, 29 Jul 2021 00:00:00 +1200https://yosgi.github.io/en/post/1104-binary-tree-pathfinding/Finding the path in a zigzag-labeled binary tree using the symmetry of each level's numbering.https://yosgi.github.io/en/post/reverse-linked-list-2/Fri, 23 Jul 2021 00:00:00 +1200https://yosgi.github.io/en/post/reverse-linked-list-2/Reversing a sublist of a linked list in place using a dummy head and tracking the boundary nodes.https://yosgi.github.io/en/post/1893-check-if-all-integers-in-the-region-are-covered/Fri, 23 Jul 2021 00:00:00 +1200https://yosgi.github.io/en/post/1893-check-if-all-integers-in-the-region-are-covered/Checking whether a set of ranges fully covers an interval, from brute force to an interval-compression optimization.https://yosgi.github.io/en/post/138-copying-a-linked-list-with-random-pointers/Thu, 22 Jul 2021 00:00:00 +1200https://yosgi.github.io/en/post/138-copying-a-linked-list-with-random-pointers/Deep-copying a linked list with random pointers using a hash map from old nodes to new.https://yosgi.github.io/en/post/684-redundant-connection/Wed, 07 Jul 2021 00:00:00 +1200https://yosgi.github.io/en/post/684-redundant-connection/Detecting the redundant edge that forms a cycle using a union-find template.https://yosgi.github.io/en/post/1202-swap-elements-in-a-string/Tue, 06 Jul 2021 00:00:00 +1200https://yosgi.github.io/en/post/1202-swap-elements-in-a-string/Producing the lexicographically smallest string after swaps by grouping swappable indices with union-find and sorting each group.https://yosgi.github.io/en/post/778-swimming-in-a-rising-pool/Mon, 05 Jul 2021 00:00:00 +1200https://yosgi.github.io/en/post/778-swimming-in-a-rising-pool/Finding the least time to swim across a rising pool by binary-searching the water level and checking reachability with DFS.https://yosgi.github.io/en/post/475-heater/Thu, 10 Jun 2021 00:00:00 +1200https://yosgi.github.io/en/post/475-heater/Finding the minimum heating radius by locating the nearest heater to each house via binary search.https://yosgi.github.io/en/post/875-keke-who-loves-bananas/Wed, 28 Apr 2021 00:00:00 +1200https://yosgi.github.io/en/post/875-keke-who-loves-bananas/Finding the minimum banana-eating speed by searching over the range of possible speeds.https://yosgi.github.io/en/post/973-k-points-closest-to-the-origin/Sat, 10 Apr 2021 00:00:00 +1200https://yosgi.github.io/en/post/973-k-points-closest-to-the-origin/Selecting the K points closest to the origin using a heap.https://yosgi.github.io/en/post/interview-question-17-14-minimum-number-of-k/Thu, 08 Apr 2021 00:00:00 +1200https://yosgi.github.io/en/post/interview-question-17-14-minimum-number-of-k/Finding the smallest K numbers in an array with a heap.https://yosgi.github.io/en/post/347-first-k-high-frequency-elements/Thu, 08 Apr 2021 00:00:00 +1200https://yosgi.github.io/en/post/347-first-k-high-frequency-elements/Finding the top K most frequent elements by counting occurrences, then selecting with a min-heap.https://yosgi.github.io/en/post/295-median-of-data-streams/Wed, 24 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/295-median-of-data-streams/Maintaining the running median of a data stream with a max-heap and a min-heap.https://yosgi.github.io/en/post/1738-find-the-k-th-largest-xor-coordinate-value/Mon, 22 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/1738-find-the-k-th-largest-xor-coordinate-value/Finding the k-th largest XOR-coordinate value with a 2D prefix-XOR DP, then selecting the k-th largest.https://yosgi.github.io/en/post/865-minimum-subtree-with-all-deepest-nodes/Sun, 21 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/865-minimum-subtree-with-all-deepest-nodes/Finding the smallest subtree containing all deepest nodes with a single bottom-up recursion that returns each subtree's depth.https://yosgi.github.io/en/post/1046-the-weight-of-the-last-stone/Sun, 21 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/1046-the-weight-of-the-last-stone/Simulating the last stone weight by repeatedly smashing the two heaviest stones with a max-heap.https://yosgi.github.io/en/post/783-binary-search-tree-node-minimum-distance/Thu, 18 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/783-binary-search-tree-node-minimum-distance/Finding the minimum distance between BST nodes using the ordered property of in-order traversal.https://yosgi.github.io/en/post/814-binary-tree-pruning/Wed, 17 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/814-binary-tree-pruning/Pruning subtrees that contain no 1 with post-order traversal, using a dummy parent so the root can also be pruned.https://yosgi.github.io/en/post/1448-count-the-number-of-good-nodes-in-a-binary-tree/Wed, 17 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/1448-count-the-number-of-good-nodes-in-a-binary-tree/Notes on counting good nodes in a binary tree using DFS with a running max.https://yosgi.github.io/en/post/1325-delete-the-leaf-node-of-the-given-value/Wed, 17 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/1325-delete-the-leaf-node-of-the-given-value/Post-order traversal approach to delete target-valued leaf nodes using a dummy root.https://yosgi.github.io/en/post/1022-the-sum-of-the-binary-numbers-from-root-to-leaf/Wed, 17 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/1022-the-sum-of-the-binary-numbers-from-root-to-leaf/Summing root-to-leaf binary numbers with top-down pre-order traversal.https://yosgi.github.io/en/post/interview-question-04-12-sum-path/Tue, 16 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/interview-question-04-12-sum-path/Counting paths with a target sum starting from any node, using an outer recursion over nodes and an inner recursion over paths.https://yosgi.github.io/en/post/563-slope-of-binary-tree/Tue, 16 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/563-slope-of-binary-tree/Computing the total tilt of a binary tree with recursion that returns each subtree's sum.https://yosgi.github.io/en/post/129-find-the-sum-of-numbers-from-the-root-node-to-the-leaf-node/Tue, 16 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/129-find-the-sum-of-numbers-from-the-root-node-to-the-leaf-node/Summing all root-to-leaf numbers with top-down pre-order DFS, carrying the running value down each path.https://yosgi.github.io/en/post/124-maximum-path-sum-in-a-binary-tree/Mon, 15 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/124-maximum-path-sum-in-a-binary-tree/Finding the maximum path sum in a binary tree with recursion that returns each node's best downward contribution.https://yosgi.github.io/en/post/99-restore-binary-search-tree/Sat, 13 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/99-restore-binary-search-tree/Restoring a BST with two swapped nodes by locating them during an in-order traversal.https://yosgi.github.io/en/post/98-verify-binary-search-tree/Sat, 13 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/98-verify-binary-search-tree/Validating a binary search tree by exploiting the increasing order of its in-order traversal.https://yosgi.github.io/en/post/863-all-nodes-with-distance-k-in-a-binary-tree/Sat, 13 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/863-all-nodes-with-distance-k-in-a-binary-tree/Finding all nodes at distance K by first adding parent links with DFS, then searching outward from the target.https://yosgi.github.io/en/post/662-binary-tree-maximum-width/Sat, 13 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/662-binary-tree-maximum-width/Computing the maximum width of a binary tree with BFS, tracking each node's position index within its level.https://yosgi.github.io/en/post/222-number-of-nodes-in-a-complete-binary-tree/Sat, 13 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/222-number-of-nodes-in-a-complete-binary-tree/Counting nodes in a complete binary tree using left/right subtree depths instead of a full DFS.https://yosgi.github.io/en/post/669-pruning-a-binary-search-tree/Thu, 11 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/669-pruning-a-binary-search-tree/Trimming a BST to a value range by recursing into the correct branch using the BST bounds.https://yosgi.github.io/en/post/450-delete-a-node-in-a-binary-search-tree/Thu, 11 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/450-delete-a-node-in-a-binary-search-tree/Deleting a node from a binary search tree by locating it via the BST property, then handling the three deletion cases.https://yosgi.github.io/en/post/116-fill-in-the-next-right-node-pointer-of-each-node/Wed, 10 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/116-fill-in-the-next-right-node-pointer-of-each-node/Connecting each node to its right neighbor per level, reusing the previous layer's links to reach constant space.https://yosgi.github.io/en/post/1008-pre-order-traversal-to-construct-a-binary-search-tree/Wed, 10 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/1008-pre-order-traversal-to-construct-a-binary-search-tree/Constructing a binary search tree from its pre-order sequence by recursively inserting each value.https://yosgi.github.io/en/post/894-all-possible-full-binary-trees/Sun, 07 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/894-all-possible-full-binary-trees/Generating all possible full binary trees with recursion that combines left and right subtree counts (DP).https://yosgi.github.io/en/post/297-serialization-and-deserialization-of-binary-trees/Thu, 04 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/297-serialization-and-deserialization-of-binary-trees/Serializing a binary tree with BFS and deserializing it using parent/child index relationships.https://yosgi.github.io/en/post/1372-longest-alternating-path-in-a-binary-tree/Mon, 01 Mar 2021 00:00:00 +1300https://yosgi.github.io/en/post/1372-longest-alternating-path-in-a-binary-tree/Finding the longest zigzag path in a binary tree with DFS that tracks direction and length, handling the boundary cases.https://yosgi.github.io/en/post/summary-of-binary-trees/Sun, 28 Feb 2021 00:00:00 +1300https://yosgi.github.io/en/post/summary-of-binary-trees/Notes on binary tree traversal — why DFS uses a stack and BFS a queue, with reusable pre/in/post-order and level-order templates.https://yosgi.github.io/en/post/133-path-sum-ii/Sun, 28 Feb 2021 00:00:00 +1300https://yosgi.github.io/en/post/133-path-sum-ii/Collecting all root-to-leaf paths with a given sum using DFS with backtracking.https://yosgi.github.io/en/post/102-level-order-traversal-of-a-binary-tree/Sun, 28 Feb 2021 00:00:00 +1300https://yosgi.github.io/en/post/102-level-order-traversal-of-a-binary-tree/Techniques and examples for breadth-first (level-order) traversal of binary trees.https://yosgi.github.io/en/post/two-color-labeling/Sat, 27 Feb 2021 00:00:00 +1300https://yosgi.github.io/en/post/two-color-labeling/A GC-inspired color-marking method that unifies iterative pre-, in-, and post-order binary tree traversal under one template.https://yosgi.github.io/en/post/145-post-order-traversal-of-a-binary-tree/Fri, 26 Feb 2021 00:00:00 +1300https://yosgi.github.io/en/post/145-post-order-traversal-of-a-binary-tree/Post-order binary tree traversal, both recursively and iteratively with a stack.https://yosgi.github.io/en/post/94-in-order-traversal-of-a-binary-tree/Thu, 25 Feb 2021 00:00:00 +1300https://yosgi.github.io/en/post/94-in-order-traversal-of-a-binary-tree/In-order binary tree traversal, both recursively and iteratively with an explicit stack.https://yosgi.github.io/en/post/215-kth-largest-element-in-an-array/Thu, 25 Feb 2021 00:00:00 +1300https://yosgi.github.io/en/post/215-kth-largest-element-in-an-array/Finding the k-th largest element with quickselect, an optimized partition-based quicksort.https://yosgi.github.io/en/post/144-pre-order-traversal-of-a-binary-tree/Thu, 25 Feb 2021 00:00:00 +1300https://yosgi.github.io/en/post/144-pre-order-traversal-of-a-binary-tree/Iterative pre-order binary tree traversal using an explicit stack.https://yosgi.github.io/en/post/105-constructing-a-binary-tree-from-pre-order-and-in-order-traversal-sequences-1/Wed, 27 Jan 2021 00:00:00 +1300https://yosgi.github.io/en/post/105-constructing-a-binary-tree-from-pre-order-and-in-order-traversal-sequences-1/Reconstructing a binary tree from its pre-order and in-order sequences by recursively splitting on the root.https://yosgi.github.io/en/post/arrays-stacks-queues/Wed, 22 Aug 2018 15:09:45 +1200https://yosgi.github.io/en/post/arrays-stacks-queues/Javascript Data Structureshttps://yosgi.github.io/en/post/javascript-sorting-algorithm/Mon, 25 Jun 2018 18:48:42 +1200https://yosgi.github.io/en/post/javascript-sorting-algorithm/Javascript algorithm sorting algorithmhttps://yosgi.github.io/en/post/set-and-map-data-structures/Wed, 02 May 2018 00:00:00 +1200https://yosgi.github.io/en/post/set-and-map-data-structures/"ES6 Standard Introduction" Knowledge Points Summary