Question

In C++. Write a program that uses array to calculate the factorial of a reasonable large number (say, up to 2,000).  

Answer 1

Program:

#include<iostream>

using namespace std;

#define size 5737 // It produce upto 5737 digits

void factorial(int n); // Function prototype

int fact(int i, int array[], int arraySize); // Function prototype

int main()

{

  int n; // variable declaration

  cout<<"Enter a number(upto 2000): ";

  cin>>n; // Accept n value

  cout<<"Factorial of "<<n<<" is:"<<endl;

  factorial(n); // calling function to find the factorial

  return 0;

}

void factorial(int n) // calling function to find factorial

{

  int array[size];

  array[0] = 1;

  int arraySize = 1;

  

  for (int i=2; i<=n; i++)

    arraySize = fact(i, array, arraySize); // recusive calling to find output size

  

  for (int j=arraySize-1; j>=0; j--)

    cout << array[j]; // print factorial using array

  cout<<endl;

}

int fact(int i, int array[], int arraySize) // calling function to find output size

{

  int check = 0;

  for (int k=0; k< arraySize; k++)

  {

int m = array[k] * i + check;

    array[k] = m % 10;

    check = m/10;

  }

  while (check)

  {

    array[arraySize] = check%10;

    check = check/10;

    arraySize++;

  }

  return arraySize;

}

Output: