0104. Maximum Depth of Binary Tree

https://leetcode.com/problems/maximum-depth-of-binary-tree

Description

Given the root of a binary tree, return its maximum depth.

A binary tree's maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

Example 1:

**Input:** root = [3,9,20,null,null,15,7]
**Output:** 3

Example 2:

**Input:** root = [1,null,2]
**Output:** 2

Example 3:

**Input:** root = []
**Output:** 0

Example 4:

**Input:** root = [0]
**Output:** 1

Constraints:

• The number of nodes in the tree is in the range [0, 104].

• -100 <= Node.val <= 100

ac

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public int maxDepth(TreeNode root) {
        int depth = 0;
        if (root == null) return 0;

        int left =  maxDepth(root.left);
        int right = maxDepth(root.right);

        return left > right ? 1 + left : 1 + right;
    }
}