2177. Find Three Consecutive Integers That Sum to a Given Number

Given an integer num, return three consecutive integers (as a sorted array) that sum to num. If num cannot be expressed as the sum of three consecutive integers, return an empty array.

class Solution {
public:
    vector<long long> sumOfThree(long long num) {
        long long start = (num - 3) / 3;
        if(start * 3 + 3 == num) {
            return {start, start + 1, start + 2};
        } else return {};
    }
};