Sometimes we need to find the divisors of a number. The first way that might come to mind is: make a reverse loop (FOR loop) and divide the number by (i) to calculate the divisors. This approach takes O(N) time.

vector<int> get_divisors_reverse(int x) {
    vector<int> divs;
    for (int i = x; i >= 1; --i) {
        if (x % i == 0) {
            divs.push_back(i);
        }
    }
    return divs;
}

But there are faster ways to calculate divisors.

This is a function that we can use to calculate the divisors of a number. Its time complexity is O(sqrt(N)).

vector<int> get_divisors(int x) {
    vector<int> divs;
    for (int i = 1; i * i <= x; ++i) {
        if (x % i == 0) {
            divs.push_back(i);
            if (i * i != x) {
                divs.push_back(x / i);
            }
        }
    }
    sort(divs.begin(), divs.end());  // Sorting is optional, depending on the requirement.
    return divs;
}

if you know fastest way share it or comment it .