FactorialBigIntegers.cpp

#include <bits/stdc++.h>
#define MAX 500
using namespace std;
int multiply(int x, int res[], int res_size);
void extraLongFactorials(int n) {
    int res[MAX]; 
    res[0] = 1; 
    int res_size = 1;
    for (int x=2; x<=n; x++) 
        res_size = multiply(x, res, res_size);
    for (int i=res_size-1; i>=0; i--) 
        cout << res[i];
}
int multiply(int x, int res[], int res_size) 
{ 
    int carry = 0;
    for (int i=0; i<res_size; i++) 
    { 
        int prod = res[i] * x + carry;  
        res[i] = prod % 10; 
        carry  = prod/10;     
    } 
    while (carry) 
    { 
        res[res_size] = carry%10; 
        carry = carry/10; 
        res_size++; 
    } 
    return res_size; 
}
int main()
{
    int n;
    cout<<"Enter the number to get factorial";
    cin >> n;
    cin.ignore(numeric_limits<streamsize>::max(), '\n');
    extraLongFactorials(n);
    return 0;
}