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Grokking the Coding Interview Patterns in C++

Solution: Lowest Common Ancestor of a Binary Tree

Explore how to identify the lowest common ancestor of two nodes in a binary tree by using a recursive depth-first search approach. Learn to track nodes and understand why a node with two true subtree hits is the ancestor. This lesson helps you implement an efficient solution in C++ with clear time and space complexity analysis.

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Statement

Given the root node of a binary tree with nn nodes, your task is to find the lowest common ancestor of two of its nodes, p and q.

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

A node can also be a descendant of itself. For example, if q is a descendant of p, and we know that p is a descendant of itself, then p will be the lowest common ancestor of p and q.

Constraints:

  • 2≤n≤5002 \leq n \leq 500
  • All Node.data are unique.
  • p
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