Factorial of a Number

Factorial of Number using Recursion

1. In this approach, we will calculate the factorial of a number using Recursion. First, we will write the base condition for recursive function, i.e., if n is equal to 0, then return 1.
2. After that, we will make the recursive call in which the function will call itself by decreasing the value of n by 1. It would look like this n*factorial(n-1)  here factorial is the function where the recursive call is being made.
3. Now in the main function, we will declare a variable named fact, and we will assign the returned value of this function factorial.

Below is the illustration of how the function will calculate the factorial of 5

Implementation in C++

// C program to calculate the factorial of a number
#include <stdio.h>

// function to make recursive calls
long factorial(long int n){
  
    //base case
    if(n==0){
        return 1;
    }

    // recursive call to calculate the factorial
    return n*factorial(n-1);
}
int main()
{
    long int n, fact;

    scanf("%d", &n);

    // storing the result from the function in the variable
    fact = factorial(n);
 
    // printing the result 
    printf("Factorial of %d is equal to %d", n, fact);

    return 0;
}

You can also try this code with Online C Compiler

Run Code

Output:

Input: N=3
Output: Factorial of 3 is equal to 6 

Complexity Analysis

Time Complexity: O(N)

Since we are making recursive calls equal to N, we can say that the time complexity would be equal to O(N).

Space Complexity: O(1)

Also see, Short int in C Programming

FAQs

1. What do you mean by the scope of the variable? What is the scope of the variable in C?
   The variable's scope may be defined as the part of the code area where the variables specified in the program can be directly accessed. Every identifier in C is lexically (or statically) scoped.
    
2. Why is C called the mother of all Languages?
   C introduced several fundamental concepts and data structures like arrays, lists, functions, strings, etc. Many languages developed after C are based on the C language. As a result, it is considered the mother of all languages.
    
3. What is the use of functions in C?
   → C functions are utilized in our application to repeatedly prevent rewriting the same code.
   → C functions can be called as many times as we want from wherever our application is.
   → When we break a program into functions, we can track any portion of our program.
   → C functions give the idea of reusability, i.e., they divide extensive work into smaller ones, making the C program more intelligible.

Key takeaways

This article discussed the problem of calculating the factorial of a number. We have discussed two approaches to this problem: the first approach using a loop and the second approach using Recursion. We have also discussed the time complexities of all the approaches. 

Also check out - Rod Cutting Problem

Also read reverse a number.

I hope you must have gained some knowledge after reading this problem, and now it is your turn to code this problem in your way. 

Until then, Keep Learning and Keep Coding.