Leetcode-对称二叉树

20.对称二叉树

题目内容：

代码及思路：

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool Symmetric(TreeNode* left,TreeNode* right)
    {
        if(left==nullptr&&right==nullptr) //如果左右子树同时为nullptr则符合题意
            return true;
        if(left==nullptr||right==nullptr)
            return false;
        if(left->val!=right->val)
            return false;
        return Symmetric(left->left,right->right)&&Symmetric(left->right,right->left);
    }
    bool isSymmetric(TreeNode* root) {
        if(root==nullptr)
            return true;
        bool res;
        res=Symmetric(root->left,root->right);
        return res;
    }
};