Today I have done leetcode's November LeetCoding Challenge with cpp.

November LeetCoding Challenge 2

Description

Count Nodes Equal to Average of Subtree

Given the root of a binary tree, return the number of nodes where the value of the node is equal to the average of the values in its subtree.

Note:

• The average of n elements is the sum of the n elements divided by n and rounded down to the nearest integer.
• A subtree of root is a tree consisting of root and all of its descendants.

Example 1:

Input: root = [4,8,5,0,1,null,6]
Output: 5
Explanation: 
For the node with value 4: The average of its subtree is (4 + 8 + 5 + 0 + 1 + 6) / 6 = 24 / 6 = 4.
For the node with value 5: The average of its subtree is (5 + 6) / 2 = 11 / 2 = 5.
For the node with value 0: The average of its subtree is 0 / 1 = 0.
For the node with value 1: The average of its subtree is 1 / 1 = 1.
For the node with value 6: The average of its subtree is 6 / 1 = 6.

Example 2:

Input: root = [1]
Output: 1
Explanation: For the node with value 1: The average of its subtree is 1 / 1 = 1.

Constraints:

• The number of nodes in the tree is in the range [1, 1000].
• 0 <= Node.val <= 1000

Solution

class Solution {
  int answer = 0;
  pair<int, int> solve(TreeNode *root) {
    if(!root) return {0, 0};
    auto [leftCount, leftSum] = solve(root->left);
    auto [rightCount, rightSum] = solve(root->right);
    int sum = root->val + leftSum + rightSum;
    int count = 1 + leftCount + rightCount;
    if(sum / count == root->val) {
      answer += 1;
    }
    return {count, sum};
  }
public:
  int averageOfSubtree(TreeNode* root) {
    solve(root);
    return answer;
  }
};

// Accepted
// 138/138 cases passed (4 ms)
// Your runtime beats 80.67 % of cpp submissions
// Your memory usage beats 34.12 % of cpp submissions (12.3 MB)