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Count Univalue Subtrees

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Description

https://leetcode.com/problems/count-univalue-subtrees/

Description

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/**
 * 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 count = 0;
        if (root == NULL) return 0;
        helper(count, root);
        return count;
    }
    
    int helper(int& count, TreeNode* root) {
        
        int leftValue = (root->left) ? helper(count, root->left) : INT_MIN;
        int rightValue = (root->right) ? helper(count, root->right) : INT_MIN;
        
        if (leftValue == INT_MAX || rightValue == INT_MAX) return INT_MAX;
        
        if ( (leftValue == INT_MIN || root->val == leftValue) &&
            (rightValue == INT_MIN || root->val == rightValue) ) {
            count += 1;
            return root->val;
        }
        
        //Failed
        return INT_MAX;
    }
};