LeetCode 543. Diameter of Binary Tree

Question

Given the root of a binary tree, return the length of the diameter of the tree.

The diameter of a binary tree is the length of the longest path between any two nodes in a tree. This path may or may not pass through the root.

The length of a path between two nodes is represented by the number of edges between them.

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

• Solution1

class Solution {
    int max = 0;
    public int diameterOfBinaryTree(TreeNode root) {
        maxDepth(root);
        return max;
    }
    
    private int maxDepth(TreeNode root) {
        if (root == null) return 0;
        int left = maxDepth(root.left);
        int right = maxDepth(root.right);
        max = Math.max(max, left + right);
        return Math.max(left, right) + 1;
    }
}

Complexity:

Time complexity: O(n)

Space complexity: O(n)