一、题目内容

二、题解

解法1：

思路

代码

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    /**
     * 递归法
     *
     * @param root
     * @return
     */
    public boolean isSymmetric(TreeNode root) {
        return root == null || check(root.left, root.right);
    }
    public boolean check(TreeNode n1, TreeNode n2) {
        if (n1 == null && n2 == null) {
            return true;
        }
        if (n1 == null || n2 == null) {
            return false;
        }
        return n1.val == n2.val && check(n1.left, n2.right) && check(n1.right, n2.left);
    }
}