p116.java

/*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
 

Constraints:

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

/**
 * 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{
            return 1+Math.max(maxDepth(root.left),maxDepth(root.right));
        }
    }
}