1582 articles
LC 114 Flatten Binary Tree to Linked List rearranges a binary tree into a right-skewed linked list in pre-order. The optimal O(1) space solution uses a Morris-like pointer manipulation trick tested at Amazon and Microsoft.
LC 116 Populate Next Right Pointers asks you to connect each node to its next right sibling. The O(1) space solution leverages already-connected next pointers on the current level to wire up the next level — a pattern tested at Amazon and Microsoft.
LC 863 All Nodes Distance K in Binary Tree finds all nodes exactly K edges from a target. The key insight is converting the tree to an undirected graph by recording parent pointers, then running BFS from the target — a pattern tested at Amazon and Google.
Solve LeetCode 129 Sum Root to Leaf Numbers with the carry-and-accumulate DFS pattern asked at Meta, Amazon, Google, and Microsoft. Includes Python and JavaScript code, dry run, and follow-ups.
Solve LeetCode 662 Maximum Width of Binary Tree with the heap-style index trick used in Amazon, Meta, and Microsoft interviews. Includes overflow-safe BFS code in Python and JavaScript.