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

May LeetCoding Challenge 18

Description

Distribute Coins in Binary Tree

You are given the root of a binary tree with n nodes where each node in the tree has node.val coins. There are n coins in total throughout the whole tree.

In one move, we may choose two adjacent nodes and move one coin from one node to another. A move may be from parent to child, or from child to parent.

Return the minimum number of moves required to make every node have exactly one coin.

Example 1:

Input: root = [3,0,0]
Output: 2
Explanation: From the root of the tree, we move one coin to its left child, and one coin to its right child.

Example 2:

Input: root = [0,3,0]
Output: 3
Explanation: From the left child of the root, we move two coins to the root [taking two moves]. Then, we move one coin from the root of the tree to the right child.

Constraints:

• The number of nodes in the tree is n.
• 1 <= n <= 100
• 0 <= Node.val <= n
• The sum of all Node.val is n.

Solution

class Solution {
public:
  int distributeCoins(TreeNode* root, TreeNode *parent = nullptr) {
    if(!root) return 0;
    int moves = distributeCoins(root->left, root) + distributeCoins(root->right, root);
    int x = root->val - 1;
    if(parent) parent->val += x;
    moves += abs(x);
    return moves;
  }
};