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250.cpp
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250.cpp
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/**
* 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:
int res = 0;
bool dfs(TreeNode* node) {
if (node == nullptr) return true;
bool left = dfs(node->left);
bool right = dfs(node->right);
if (left && right) {
if ((node->left == nullptr || node->val == node->left->val)
&& (node->right == nullptr || node->val == node->right->val)) {
res++;
return true;
}
else return false;
}
return false;
}
int countUnivalSubtrees(TreeNode* root) {
dfs(root);
return res;
}
};