0104 - Maximum Depth of Binary Tree

0104 - Maximum Depth of Binary Tree

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.

Examples

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

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

Input: root = [] Output: 0

Input: root = [0] Output: 1

Constraints

The number of nodes in the tree is in the range [0, 104]. -100 <= Node.val <= 100

Java Solution

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public int maxDepth(TreeNode root) {
        if(root == null) return 0;
        else {
            int leftHeight = maxDepth(root.left);
            int rightHeight = maxDepth(root.right);
            
            return Math.max(leftHeight, rightHeight) + 1;
        }
    }

}