maximum-depth-of-binary-tree.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(int x) { val = x; }
 * }
 */
class Solution {
    public int maxDepth(TreeNode root) {
    if (root == null) return 0;
    return 1 + (Math.max(maxDepth(root.left), maxDepth(root.right)));
    }
}