Distribute candies in a binary tree.cpp

class Solution
{
public:
    int solve(Node* root, int& moves)
    {
        if (!root)
        {
            return 0;
        }

        int left = solve(root->left, moves);
        int right = solve(root->right, moves);
        moves += abs(left) + abs(right);

        return root->key - 1 + left + right;
    }
    int distributeCandy(Node* root)
    {
        int moves = 0;
        solve(root, moves);
        return moves;
    }
};