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Grokking the Coding Interview Patterns in Go

Solution: Lowest Common Ancestor of a Binary Tree III

Explore the method to find the lowest common ancestor of two nodes in a binary tree when only parent pointers are available. Learn how to use two pointers that traverse upward and switch starting points to efficiently identify the common ancestor without requiring the tree root. Understand the time and space efficiency of this approach and apply it to solve similar problems effectively.

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Statement

You are given two nodes, p and q. The task is to return their lowest common ancestor (LCA). Both nodes have a reference to their parent node. The tree’s root is not provided; you must use the parent pointers to find the nodes’ common ancestor.

Note: The lowest common ancestor of two nodes, p and q, is the lowest node in the binary tree, with both p and q as descendants.

In a tree, a descendant of a node is any node reachable by following edges downward from that node, including the node itself. ...