Calculating The Factorial Of A Number in C#

The factorial of a non-negative integer 𝑛 n is the product of all positive integers less than or equal t 𝑛. It is denoted by 𝑛!.

Definition

 n!=n×(n−1)×(n−2)×…×2×1  

Examples

 5!=5×4×3×2×1=120  
 3!=3×2×1=6  
 1!=1  
 0!=1  

Calculating The Factorial Of A Number

Calculating the factorial of a number in C# can be done using either an iterative or a recursive approach. Here are examples of both methods:

Iterative Approach

 using System;  
 class Program  
 {  
   static void Main()  
   {  
     Console.Write("Enter a number: ");  
     int number = int.Parse(Console.ReadLine());  
     long factorial = Factorial(number);  
     Console.WriteLine($"Factorial of {number} is {factorial}");  
   }  
   static long Factorial(int n)  
   {  
     long result = 1;  
     for (int i = 1; i <= n; i++)  
     {  
       result *= i;  
     }  
     return result;  
   }  
 }  

Recursive Approach

 using System;  
 class Program  
 {  
   static void Main()  
   {  
     Console.Write("Enter a number: ");  
     int number = int.Parse(Console.ReadLine());  
     long factorial = Factorial(number);  
     Console.WriteLine($"Factorial of {number} is {factorial}");  // Result of factoriale
   }  
   static long Factorial(int n)  
   {  
     if (n == 0 || n == 1)  
       return 1;  
     return n * Factorial(n - 1);  
   }  
 }  

Explanation

• Iterative Approach: Uses a loop to multiply numbers from 1 to n.
• Recursive Approach: Calls itself with decremented values until it reaches the base case.

Usage of Factori l Number

You can run either of these programs in a C# environment. Just input a non-negative integer, and it will calculate the factorial. Keep in mind that for larger values of n, the result can exceed the range of long, so consider using BigInteger for very large factorials:

 using System;  
 using System.Numerics;  
 class Program  
 {  
   static void Main()  
   {  
     Console.Write("Enter a number: ");  
     int number = int.Parse(Console.ReadLine());  
     BigInteger factorial = Factorial(number);  
     Console.WriteLine($"Factorial of {number} is {factorial}");  
   }  
   static BigInteger Factorial(int n)  
   {  
     if (n == 0 || n == 1)  
       return 1;  
     return n * Factorial(n - 1);  
   }  
 }  

Thanks