543. Diameter of Binary Tree

https://leetcode.com/problems/diameter-of-binary-tree/

Python

DFS

class Solution:
    def diameterOfBinaryTree(self, root: Optional[TreeNode]) -> int:
        ans = 0
        def dfs(node):
            if not node:
                return 0
            nonlocal ans
            left_depth = dfs(node.left)
            right_depth = dfs(node.right)
            ans = max(ans, left_depth+right_depth)
            return 1 + max(left_depth, right_depth)

        dfs(root)

        return ans