Need help creating a program to factorize numbers

Question

The task is to create a program that can do the maximum factorial possible by the machine using "for" cycle.

I understood i have to use bigger data types (the biggest one is "long long", correct me if i'm wrong), and i also understood the concept of the factorial.

Otherwise, i really do not know how to apply what i know in c++.

these is the idea at the base of what i wrote down as of now:

#include <cstdlib>
#include <iostream>
#include <math.h>

include namespace std;

int main(int argc, char *argv[])

{
   long long i, factorial;
   cin<<factorial;

   {
      for(long long i=1; i=factorial; i++)
      {
         factorial=factorial*i
      }
   }

  system("PAUSE");
  return EXIT_SUCCESS;
}

Problems are:

1. I don't know if the code it's wrote correctly
2. by doing "factorial=factorial*i", the "i=factorial" in the "for" cycle doesn't make sense, since it will stop the program before it has to.

This being said, I would like to point out that i am in high school, my programming knowledge is really poor, and for this reason every kind of advice and information is very well accepted :).

Thanks in advance

Answer 1

Maybe you want to compute the maximum factorial that will fit in an unsigned long long data type.

But let us look at the horrible program. I add comments with the problems.

#include <cstdlib> // Not to be used in C++
#include <iostream>
#include <math.h>   // Not needed

include namespace std;   // Completely wrong statement. But even if you would have done it syntactically correct, it should never be used

int main(int argc, char *argv[]) // Neither args nor argv is used
{
   long long i, factorial; // i will be redefine later. factorial is not initialized
   cin<<factorial;  // You want to stream somethin into std::cin?

   {
      for(long long i=1; i=factorial; i++) // Thats heavy stuff. i=factorial? Nobody know, what will happen
      {
         factorial=factorial*i   // Semicolon missing
      }
   }

  system("PAUSE");  // Do not use in C++
  return EXIT_SUCCESS;   // EXIT_SUCCESS is not defined
}

Maybe the below could give you an idea

#include <iostream>

int main() {
    unsigned long long number{};
    unsigned long long factorial{1};

    std::cin >> number;

    for (unsigned long long i{ 1 }; i <= number; ++i)
        factorial = factorial * i;

    std::cout << factorial;
}