Lowest Common Ancestor in BST

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Solution Guide: Lowest Common Ancestor in BST

Approach

For BST, both keys below go left, both above go right; otherwise current node is LCA.

Complexity Analysis

Time
O(h) where h is tree height
Space
O(h) recursion depth

Pattern

BST Guided Search

Why It Works

BST ordering guarantees the split of target nodes into left or right partitions.

Updated Feb 2026