C++ Program to Find Factorial

Factorial of a non-negative integer n is the product of all the positive integers that are less than or equal to n.

For example: The factorial of 5 is 120.

5! = 5 * 4 * 3 * 2 *1
5! = 120

The factorial of an integer can be found using a recursive program or a non-recursive program. Example of both of these are given as follows.

Factorial using Non-Recursive Program

A for loop can be used to find the factorial of a number. This is demonstrated using the following program −

Example

 Live Demo

#include <iostream>
using namespace std;
int main() {
   int n = 5, fact = 1, i;
   for(i=1; i<=n; i++)
   fact = fact * i;
   cout<<"Factorial of "<<n<<" is "<<fact;
   return 0;
}

Output

Factorial of 5 is 120

In the above program, the for loop runs from 1 to n. For each iteration of the loop, fact is multiplied with i. The final value of fact is the product of all numbers from 1 to n. This is demonstrated using the following code snippet.

for(i=1; i<=n; i++)
fact = fact * i;

Factorial Using a Recursive Program

The following program demonstrates a recursive program to find the factorial of a number.

Example

 Live Demo

#include <iostream>
using namespace std;
int fact(int n) {
   if ((n==0)||(n==1))
   return 1;
   else
   return n*fact(n-1);
}
int main() {
   int n = 5;
   cout<<"Factorial of "<<n<<" is "<<fact(n);
   return 0;
}

Output

Factorial of 5 is 120

In the above program, the function fact() is a recursive function. The main() function calls fact() using the number whose factorial is required. This is demonstrated by the following code snippet.

cout<<"Factorial of "<<n<<" is "<<fact(n);

If the number is 0 or 1, then fact() returns 1. If the number is any other, then fact() recursively calls itself with the value n-1.

This is demonstrated using the following code snippet −

int fact(int n) {
   if ((n==0)||(n==1))
   return 1;
   else
   return n*fact(n-1);
}