C Program for factorial of a number

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

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

#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));
    }
}


Output:
Factorial is 5 is 120

Iterative Solution:
Factorial can also be calculated iteratively as recursion can be costly for large numbers.

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 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));
    }
}


Output:
Factorial of 5 is 120

Time complexity of the above solutions is O(n).

Please write comments if you find any bug in above code/algorithm, or find other ways to solve the same problem.

GATE CS Corner    Company Wise Coding Practice

Recommended Posts:







Writing code in comment? Please use ide.geeksforgeeks.org, generate link and share the link here.