leetcode日记（88）对称二叉树

和上一题没什么区别，学会用简洁易懂一点的方法了（！

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    bool issmmety(TreeNode* left,TreeNode* right){
        if(left==NULL||right==NULL) return right==NULL&&left==NULL;
        if(left->val!=right->val) return 0;
        else return issmmety(left->left,right->right)&&issmmety(left->right,right->left);
    }
    bool isSymmetric(TreeNode* root) {
        return issmmety(root->left,root->right);
    }
};