Leetcode 250. Count Univalue Subtrees (Medium) (cpp)
Tag: Tree
Difficulty: Medium
/* 250. Count Univalue Subtrees (Medium) Given a binary tree, count the number of uni-value subtrees. A Uni-value subtree means all nodes of the subtree have the same value. For example: Given binary tree, 5 / \ 1 5 / \ \ 5 5 5 return 4. */ /** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ class Solution { public: int countUnivalSubtrees(TreeNode* root) { int res = 0; cout(root, res); return res; } private: int cout(TreeNode* root, int& res) { if (root == NULL) { return 0; } else if (root->left == NULL && root->right == NULL) { res++; return 1; } int l = cout(root->left, res), r = cout(root->right, res); if (l == 1 && r == 1) { if (root->val == root->left->val && root->val == root->right->val) { res += 1; return 1; } } else if (l == -1 || r == -1) { return -1; } else if (l != 0 && root->val == root->left->val) { res += 1; return 1; } else if (r != 0 && root->val == root->right->val) { res += 1; return 1; } return -1; } };