dsa1 min read
Construct Binary Tree from Preorder and Inorder — HashMap Index
Build a binary tree from preorder and inorder traversals by using the preorder root and inorder index to split left/right subtrees.
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Path Sum III — Prefix Sum HashMap on Tree
Count paths in a binary tree summing to target (not necessarily root-to-leaf) using a prefix sum frequency map.
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dsa3 min read
Delete Node in a BST
Find and delete a node from a BST while maintaining BST properties using in-order successor.
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Flatten Binary Tree to Linked List
Flatten a binary tree to a linked list in-place using pre-order traversal order.
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Populating Next Right Pointers in Each Node
Connect each node to its next right node using BFS level order or O(1) space pointer manipulation.
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