LintCode 97---二叉树的最大深度

/**
 * Definition of TreeNode:
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left, right;
 *     public TreeNode(int val) {
 *         this.val = val;
 *         this.left = this.right = null;
 *     }
 * }
 */

public class Solution {
    /**
     * @param root: The root of binary tree.
     * @return: An integer
     */
    public int maxDepth(TreeNode root) {
        // write your code here
    if(root==null) return 0;

    int left=maxDepth(root.left);
    int right=maxDepth(root.right);
    return 1+Math.max(left,right);
    }
}