LeetCode 250. Count Univalue
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.
Example :
Input: root = [5,1,5,5,5,null,5]
5
/
1 5
/ \
5 5 5
Output: 4
解法1：
因为是premium的题目，我在www.codingninjas.com上做的。
/*************************************************************Following is the Binary Tree node structureclass BinaryTreeNode {public : T data;BinaryTreeNode<T> *left;BinaryTreeNode<T> *right;BinaryTreeNode(T data) {this -> data = data;left = NULL;right = NULL;}};*************************************************************/int count = 0;
int helper(BinaryTreeNode<int> *root) {if (!root) return -100;if (!root->left && !root->right) {count++;return root->data;}int left = helper(root->left);int right = helper(root->right);if (left != right) {if (left != -100 && right != -100) return -200;}if (left == root->data || right == root->data) {count++;return root->data;}return -300;
}int countUnivalTrees(BinaryTreeNode<int> *root)
{// Write your code here.count=0; //这行可能不需要，但是codingninjas的环境好像有点问题，每个测试用例都需要清零一下。helper(root);return count;
}
)
