Leet Code OJ 101. Symmetric Tree [Difficulty: Easy]

题目：
Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).

For example, this binary tree is symmetric:

But the following is not:

Note:
Bonus points if you could solve it both recursively and iteratively.

翻译：
给定一个二叉树，检测它是不是一个它自己的镜像（左右对称）。

代码：

/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */
public class Solution {
    public boolean isSymmetric(TreeNode root) {
        if(root==null){
            return true;
        }else{
            return isSame(root.left,root.right);
        }

    }
    public boolean isSame(TreeNode left,TreeNode right) {
        if(left==null&&right==null){
            return true;
        }else if(left!=null&&right!=null){
            if(left.val!=right.val){
                return false;
            }
            boolean res1=isSame(left.left,right.right);
            boolean res2=isSame(left.right,right.left);
            if(res1&&res2){
                return true;
            }else{
                return false;
            }
        }else{
            return false;
        }
    }
}