Factorial digital solution [Written by Roland Ihasz , 10th October 2019]

FuncSolution.cpp

// Title: Factorial digital solution 
// 10th Oct 2019 
// Written by Roland Ihasz

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

typedef std::vector<unsigned int> Digits;

Digits factorial(unsigned int maxFactor)
{
    Digits result = { 1 };

    result.reserve(2568); 

    for(unsigned int factor = 2; factor <= maxFactor; factor++) {
        unsigned int carry = 0;
        for(auto &digit : result) {
            digit = digit * factor + carry;

            if(digit >= 10) {
                carry  = digit / 10;
                digit %= 10;
            }
            else {
                carry  = 0;
            }
        }

        while(carry != 0) {
            result.push_back(carry % 10);
            carry /= 10;
        }
    }
    return result;
}

int main()
{
    unsigned int tests;
    std::cin >> tests;
    while(tests--) {
        unsigned int number;
        std::cin >> number;

        unsigned int sum = 0;
        for(auto i : factorial(number)) {
            sum += i;
        }
        std::cout << sum << std::endl;
    }
    return 0;
}