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

MaximumDepthOfBinaryTree.java

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public int maxDepth(TreeNode root) {
        if (root == null){
            return 0;
        } else {
            int left = maxDepth(root.left);
            int right = maxDepth(root.right);
            int ret;
            if (left > right){
                ret = left + 1;
            } else {
                ret = right + 1;
            }
            return ret;
        }
    }
}