Factorial program in C++

Factorial Program in C++: Factorial of n is the product of all positive descending integers. Factorial of n is denoted by n!. For example:

4! = 4*3*2*1 = 24  

6! = 6*5*4*3*2*1 = 720

Here, 4! is pronounced as "4 factorial", it is also called "4 bang" or "4 shriek".

The factorial is normally used in Combinations and Permutations (mathematics).

There are many ways to write the factorial program in C++ language. Let's see the 2 ways to write the factorial program.

• Factorial Program using loop
• Factorial Program using recursion

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Factorial Program using Loop

Let's see the factorial Program in C++ using loop.

#include <iostream>  
using namespace std;  
int main()  
{  
   int i,fact=1,number;    
  cout<<"Enter any Number: ";    
 cin>>number;    
  for(i=1;i<=number;i++){    
      fact=fact*i;    
  }    
  cout<<"Factorial of " <<number<<" is: "<<fact<<endl;  
  return 0;  
} 

Output:

Enter any Number: 5  
Factorial of 5 is: 120  

Factorial Program using Recursion

Let's see the factorial program in C++ using recursion.

#include<iostream>    
using namespace std;      
int main()    
{    
int factorial(int);    
int fact,value;    
cout<<"Enter any number: ";    
cin>>value;    
fact=factorial(value);    
cout<<"Factorial of a number is: "<<fact<<endl;    
return 0;    
}    
int factorial(int n)    
{    
if(n<0)    
return(-1); /*Wrong value*/      
if(n==0)    
return(1);  /*Terminating condition*/    
else    
{    
return(n*factorial(n-1));        
}    
}

Output:

Enter any number: 6   
Factorial of a number is: 720