/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    bool isSymmetric(TreeNode *root) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        if(root==NULL)        return true;        vector
     
       left;        vector
      
        right;        vector
       
         templ;        vector
        
          tempr;        templ.push_back(root);        tempr.push_back(root);        while(!templ.empty()&&!tempr.empty())        {            vector
         
           prel;            vector
          
            prer; int size = tempr.size(); for(int i = 0;i < size;i++) { if(templ[i]->left != NULL) { if(tempr[i]->right == NULL) return false; else if(tempr[i]->right->val == templ[i]->left->val) { prer.push_back(tempr[i]->right); prel.push_back(templ[i]->left); } else { return false; } } if(templ[i]->right != NULL) { if(tempr[i]->left == NULL) return false; else if(templ[i]->right->val == tempr[i]->left->val) { prer.push_back(tempr[i]->left); prel.push_back(templ[i]->right); } else { return false; } } } templ = prel; tempr = prer; } return true; }};