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Tree•Pattern: Post-order DFS•Medium

Diameter of a binary tree

Problem Intuition & Objective

Find the length of the longest path between any two nodes (may not pass through root).

Time ComplexityO(n)
Optimal
Space ComplexityO(h)
Memory Bounds
Optimal Algorithmic Approach

Post-order DFS: each node returns its height; update global diameter.

Core Invariants & Edge Cases

  • At each node compute height of left and right subtrees
  • Diameter through this node = leftHeight + rightHeight
  • Track global maximum as you recurse
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