1 class Solution {

 2 public:

 3     int flag = 0;

 4     bool isUnivalTree(TreeNode* root){

 5         isUnivalTree1(root,root->val);

 6         if(flag == 0) return true;

 7         else return false;

 8     }

 9     void isUnivalTree1(TreeNode* root,int tmp) {

10         if(root!=NULL){

11             isUnivalTree1(root->left,tmp);

12             if(root->val != tmp) flag = 1;

13             isUnivalTree1(root->right,tmp);

14

15         }

16     }

17 };