BST

Subtitle / Summary The key to LeetCode 108 is not recursion by itself. It is noticing that the problem wants two things at the same time: BST ordering and height balance. Once you read those two constraints together, “pick the middle element as the root” stops being a trick and becomes the natural construction rule. Reading time: 11-14 min Tags: Hot100, binary tree, BST, divide and conquer, recursion SEO keywords: Convert Sorted Array to Binary Search Tree, BST, balanced BST, divide and conquer, recursion, LeetCode 108 Meta description: Learn LeetCode 108 from the midpoint-construction idea, with step-by-step derivation, engineering mappings, and runnable multi-language implementations. A — Algorithm Problem Restatement Given an integer array nums sorted in strictly increasing order, convert it into a height-balanced binary search tree. ...

Subtitle / Summary LeetCode 230 is not really about tree traversal mechanics alone. It is about turning BST order into a useful query. Once you see that the k-th smallest value is simply the k-th node visited in inorder traversal, the problem becomes a very stable counting task. Reading time: 11-14 min Tags: Hot100, binary tree, BST, inorder traversal, stack SEO keywords: Kth Smallest Element in a BST, BST, inorder traversal, stack, LeetCode 230 Meta description: Learn LeetCode 230 from BST inorder ordering, explicit-stack counting, and early-stop traversal, with runnable multi-language implementations. A — Algorithm Problem Restatement Given the root root of a binary search tree and an integer k, return the k-th smallest value in the tree. ...

Subtitle / Summary The hardest part of LeetCode 98 is usually not recursion itself. It is realizing that checking a node against only its parent is not enough. A valid BST is constrained by all of its ancestors, so the stable solution is to pass a valid range downward. This guide explains that idea from scratch, then connects it to the equivalent inorder-sorted view. Reading time: 11-13 min Tags: Hot100, binary tree, BST, DFS, inorder traversal SEO keywords: Validate Binary Search Tree, BST, range constraints, inorder traversal, DFS, LeetCode 98 Meta description: Learn LeetCode 98 from the core invariant low < val < high, with step-by-step derivation, engineering mappings, and runnable multi-language implementations. A — Algorithm Problem Restatement Given the root root of a binary tree, determine whether it is a valid binary search tree (BST). ...