https://leetcode.com/problems/univalued-binary-tree/

1. Use recursion

  1. //0 ms    8.6 MB
  3. /**
  4.  * Definition for a binary tree node.
  5.  * struct TreeNode {
  6.  *     int val;
  7.  *     TreeNode *left;
  8.  *     TreeNode *right;
  9.  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
  10.  * };
  11.  */
  12. class Solution {
  13. public:
  14.     bool isUnivalTree(TreeNode* root) {
  15.         if(!root) return true;
  17.         bool unival = true;
  19.         if( (root->left && root->val != root->left->val) ||
  20.            (root->right && root->val != root->right->val) )
  21.             unival = false;
  23.         return unival && isUnivalTree(root->left) && isUnivalTree(root->right);
  24.     }
  25. };