Skip to content
Related Articles

Related Articles

Program for factorial of a number

View Discussion
Improve Article
Save Article
Like Article
  • Difficulty Level : Basic
  • Last Updated : 21 Jun, 2022

Factorial of a non-negative integer, is multiplication of all positive integers smaller than or equal to n. For example factorial of 6 is 6*5*4*3*2*1 which is 720. 

A factorial is represented by a number and a  ” ! ”  mark at the end. It is widely used in permutations and combination to calculate the total possible outcomes. A French mathematician Christian Kramp firstly used  the exclamation. 
 

Recursive Solution: 
Factorial can be calculated using following recursive formula. 
 

  n! = n * (n-1)!
  n! = 1 if n = 0 or n = 1

 

Following is implementation of factorial. 
 

C++




// C++ program to find factorial of given number
#include <iostream>
using namespace std;
 
// function to find factorial of given number
unsigned int factorial(unsigned int n)
{
    if (n == 0)
        return 1;
    return n * factorial(n - 1);
}
 
// Driver code
int main()
{
    int num = 5;
    cout << "Factorial of "
         << num << " is " << factorial(num) << endl;
    return 0;
}
 
// This code is contributed by Shivi_Aggarwal

C




// C program to find factorial of given number
#include <stdio.h>
 
// function to find factorial of given number
unsigned int factorial(unsigned int n)
{
    if (n == 0)
        return 1;
    return n * factorial(n - 1);
}
 
int main()
{
    int num = 5;
    printf("Factorial of %d is %d", num, factorial(num));
    return 0;
}

Java




// Java program to find factorial of given number
class Test {
    // method to find factorial of given number
    static int factorial(int n)
    {
        if (n == 0)
            return 1;
 
        return n * factorial(n - 1);
    }
 
    // Driver method
    public static void main(String[] args)
    {
        int num = 5;
        System.out.println("Factorial of " + num
                           + " is " + factorial(5));
    }
}

Python3




# Python 3 program to find
# factorial of given number
 
# Function to find factorial of given number
def factorial(n):
      
    if n == 0:
        return 1
     
    return n * factorial(n-1)
  
# Driver Code
num = 5;
print("Factorial of", num, "is",
factorial(num))
  
# This code is contributed by Smitha Dinesh Semwal

C#




// C# program to find factorial
// of given number
using System;
 
class Test {
    // method to find factorial
    // of given number
    static int factorial(int n)
    {
        if (n == 0)
            return 1;
 
        return n * factorial(n - 1);
    }
 
    // Driver method
    public static void Main()
    {
        int num = 5;
        Console.WriteLine("Factorial of "
                          + num + " is " + factorial(5));
    }
}
 
// This code is contributed by vt_m

PHP




<?php
// PHP program to find factorial
// of given number
 
// function to find factorial
// of given number
function factorial($n)
{
    if ($n == 0)
        return 1;
    return $n * factorial($n - 1);
}
 
    // Driver Code
    $num = 5;
    echo "Factorial of ", $num, " is ", factorial($num);
 
// This code is contributed by m_kit
?>

Javascript




<script>
// Javascript to find factorial
// of given number
 
// function to find factorial
// of given number
function factorial(n) {
  if (n == 0) return 1;
  return n * factorial(n - 1);
}
 
// Driver Code
let num = 5;
document.write("Factorial of " + num + " is " + factorial(num));
 
// This code is contributed by Saurabh Jaiswal
 
</script>

Output: 

Factorial of 5 is 120

Iterative Solution: 
Factorial can also be calculated iteratively as recursion can be costly for large numbers. Here we have shown the iterative approach using both for and while loop. 
Using For loop 
 

C++




// C++ program for factorial of a number
#include <iostream>
using namespace std;
 
// function to find factorial of given number
unsigned int factorial(unsigned int n)
{
    int res = 1, i;
    for (i = 2; i <= n; i++)
        res *= i;
    return res;
}
 
// Driver code
int main()
{
    int num = 5;
    cout << "Factorial of "
         << num << " is "
         << factorial(num) << endl;
    return 0;
}
 
// This code is contributed by Shivi_Aggarwal

C




#include <stdio.h>
 
// function to find factorial of given number
unsigned int factorial(unsigned int n)
{
    int res = 1, i;
    for (i = 2; i <= n; i++)
        res *= i;
    return res;
}
 
int main()
{
    int num = 5;
    printf(
        "Factorial of %d is %d", num, factorial(num));
    return 0;
}

Java




// Java program to find factorial of given number
class Test {
 
    // Method to find factorial of the given number
    static int factorial(int n)
    {
        int res = 1, i;
        for (i = 2; i <= n; i++)
            res *= i;
        return res;
    }
 
    // Driver method
    public static void main(String[] args)
    {
        int num = 5;
        System.out.println(
            "Factorial of " + num
            + " is " + factorial(5));
    }
}

Python3




# Python 3 program to find
# factorial of given number
 
# Function to find factorial of given number
def factorial(n):
      
    res = 1
     
    for i in range(2, n+1):
        res *= i
    return res
 
# Driver Code
num = 5;
print("Factorial of", num, "is",
factorial(num))
  
# This code is contributed by Smitha Dinesh Semwal

C#




// C# program to find
// factorial of given number
using System;
 
class Test {
    // Method to find factorial
    // of given number
    static int factorial(int n)
    {
        int res = 1, i;
 
        for (i = 2; i <= n; i++)
            res *= i;
        return res;
    }
 
    // Driver method
    public static void Main()
    {
        int num = 5;
        Console.WriteLine(
            "Factorial of " + num
            + " is " + factorial(5));
    }
}
 
// This code is contributed by vt_m

PHP




<?php
 
// function to find factorial
// of given number
function factorial( $n)
{
    $res = 1; $i;
    for ($i = 2; $i <= $n; $i++)
        $res *= $i;
    return $res;
}
 
// Driver Code
$num = 5;
echo "Factorial of ", $num, " is ",
                    factorial($num);
 
// This code is contributed
// by anuj_67.
?>

Javascript




<script>
// JavaScript program to find factorial of given number
 
    // Method to find factorial of the given number
    function factorial(n)
    {
        var res = 1, i;
        for (i = 2; i <= n; i++)
            res *= i;
        return res;
    }
 
    // Driver method
     
        var num = 5;
        document.write("Factorial of " + num + " is " + factorial(5));
 
 
// This code is contributed by shivanisinghss2110.
 
</script>

Output : 
 

Factorial of 5 is 120

Using While loop 
 

C




// C program for factorial of a number
#include <stdio.h>
 
// function to find factorial of given number
unsigned int factorial(unsigned int n)
{
     if(n == 0)
          return 1;
    int i = n, fact = 1;
    while (n / i != n) {
        fact = fact * i;
        i--;
    }
    return fact;
}
 
int main()
{
    int num = 5;
    printf("Factorial of %d is %d", num, factorial(num));
    return 0;
}

C++




// C++ program for factorial of a number
#include <iostream>
using namespace std;
 
// function to find factorial of given
// number using while loop
unsigned int factorial(unsigned int n)
{
    if(n == 0)
          return 1;
    int i = n, fact = 1;
    while (n / i != n) {
        fact = fact * i;
        i--;
    }
    return fact;
}
 
// Driver code
int main()
{
    int num = 5;
    cout << "Factorial of "
         << num << " is "
         << factorial(num) << endl;
    return 0;
}
// This code is contributed by Shivi_Aggarwal

Java




// Java program to find factorial of given number
 
class Test {
 
    // Method to find factorial of the given number
    static int factorial(int n)
    {
        if(n == 0)
           return 1;
        int i = n, fact = 1;
        while (n / i != n) {
            fact = fact * i;
            i--;
        }
        return fact;
    }
 
    // Driver method
    public static void main(String[] args)
    {
        int num = 5;
        System.out.println(
            "Factorial of " + num
            + " is " + factorial(5));
    }
}

Python3




# Python 3 program to find
# factorial of given number
 
# Function to find factorial of given number
def factorial(n):
    if(n == 0):
       return 1
    i = n
    fact = 1
     
    while(n / i != n):
        fact = fact * i
        i -= 1
         
    return fact
 
# Driver Code
num = 5;
print("Factorial of", num, "is",
factorial(num))
  
# This code is contributed by Smitha Dinesh Semwal

C#




// C# program to find
// factorial of given number
using System;
 
class Test {
    // Method to find factorial
    // of given number
    static int factorial(int n)
    {
        if(n == 0)
            return 1;
        int i = n, fact = 1;
        while (n / i != n) {
            fact = fact * i;
            i--;
        }
        return fact;
    }
 
    // Driver method
    public static void Main()
    {
        int num = 5;
        Console.WriteLine(
            "Factorial of " + num
            + " is " + factorial(5));
    }
}

Javascript




<script>
        // JavaScript Program to implement
        // the above approach
        // function to find factorial of given
        // number using while loop
        function factorial(n) {
            if (n == 0)
                return 1;
            let i = n, fact = 1;
            while (Math.floor(n / i) != n) {
                fact = fact * i;
                i--;
            }
            return fact;
        }
 
        // Driver code
        let num = 5;
        document.write("Factorial of "
            + num + " is "
            + factorial(num) + "<br>");
 
// This code is contributed by Potta Lokesh
 
    </script>

Output : 
 

Factorial of 5 is 120

Time complexity of the above iterative solutions is O(n).
One line Solution (Using Ternary operator): 
 

C++




// C++ program to find factorial of given number
#include <iostream>
using namespace std;
 
int factorial(int n)
{
    // single line to find factorial
    return (n == 1 || n == 0) ? 1 : n * factorial(n - 1);
}
 
// Driver Code
int main()
{
    int num = 5;
    cout << "Factorial of " << num << " is "<< factorial(num);
    return 0;
}
 
// This code is contributed by shivanisinghss2110

C




// C++ program to find factorial of given number
#include <stdio.h>
 
int factorial(int n)
{
    // single line to find factorial
    return (n == 1 || n == 0) ? 1 : n * factorial(n - 1);
}
 
// Driver Code
int main()
{
    int num = 5;
    printf("Factorial of %d is %d", num, factorial(num));
    return 0;
}
 
// This code is contributed by  Rithika palaniswamy.

Java




// Java program to find factorial
// of given number
class Factorial {
 
    int factorial(int n)
    {
 
        // single line to find factorial
        return (n == 1 || n == 0) ? 1 : n * factorial(n - 1);
    }
 
    // Driver Code
    public static void main(String args[])
    {
        Factorial obj = new Factorial();
        int num = 5;
        System.out.println(
            "Factorial of " + num
            + " is " + obj.factorial(num));
    }
}
 
// This code is contributed by Anshika Goyal.

Python3




# Python 3 program to find
# factorial of given number
 
def factorial(n):
 
    # single line to find factorial
    return 1 if (n == 1 or n == 0) else n * factorial(n - 1)
 
 
# Driver Code
num = 5
print ("Factorial of", num, "is",
      factorial(num))
 
# This code is contributed
# by Smitha Dinesh Semwal.

C#




// C# program to find factorial
// of the given number
using System;
 
class Factorial {
 
    int factorial(int n)
    {
 
        // single line to find factorial
        return (n == 1 || n == 0) ? 1 : n * factorial(n - 1);
    }
 
    // Driver Code
    public static void Main()
    {
        Factorial obj = new Factorial();
        int num = 5;
 
        Console.WriteLine(
            "Factorial of " + num
            + " is " + obj.factorial(num));
    }
}
 
// This code is contributed by vt_m.

PHP




<?php
// PHP program to find factorial
// of given number
 
function factorial( $n)
{
     
    // single line to find factorial
    return ($n == 1 || $n == 0) ? 1:
             $n * factorial($n - 1);
}
 
    // Driver Code
    $num = 5;
    echo "Factorial of ", $num, " is ", factorial($num);
 
// This code is contributed by anuj_67.
?>

Javascript




<script>
 
// JavaScript program to find factorial of given number
function factorial(n)
{
    // single line to find factorial
    return (n == 1 || n == 0) ? 1 : n * factorial(n - 1);
}
 
// Driver Code
 
    var num = 5;
    document.write("Factorial of " +num +" is " + factorial(num));
 
// This code is contributed by shivanisinghss2110.
 
</script>

Output: 

Factorial of 5 is 120

Problems in writing code of factorial

When the value of n changes increases by 1, the value of the factorial increases by n. So the variable storing the value of factorial should have a large size. Following is the value of n whose factorial can be stored in the respective size.

1. integer –> n<=12

2. long long int –> n<=19

From the above data, we can see that a very small value of n can be calculated because of the faster growth of the factorial function. We can however find the mod value of factorial of larger values by taking mod at each step.

The above solution cause overflow for large numbers. Please refer factorial of large number for a solution that works for large numbers.
Please write comments if you find any bug in the above code/algorithm, or find other ways to solve the same problem.
 


My Personal Notes arrow_drop_up
Recommended Articles
Page :

Start Your Coding Journey Now!