18. C Recursion.md

C Recursion

Video Link: https://youtu.be/61T0cZ8KyGM
Tutorial Link: https://www.programiz.com/c-programming/c-recursion

Example: C Recursion

#include <stdio.h>
int sum(int n);

int main() {
    int number, result;

    printf("Enter a positive integer: ");
    scanf("%d", &number);

    result = sum(number);

    printf("sum = %d", result);
    return 0;
}

int sum(int n) {
    if (n != 0) {
        // sum() function calls itself
        return n + sum(n-1); 
    }  
    else {
        return n;
    }
}

Output

Enter a positive integer: 4
sum = 10

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Programming Task

Create a program that computes the factorial of a number.

• Take an input number from the user
• Create a function that takes the number as a parameter.
• Inside the function check if the number is greater than 0.
• If true, return number multiplied by a recursive call to the function with parameter 1 less than number
• Else, return 1

Solution :

#include <stdio.h>

int fact (int n);

int main() {
    
    int number;
    printf("Enter any number: ");
    scanf("%d", &number);
    
    if(number > 0) {
        int result = fact(number);
        printf("The Factorial is : %d", result);
    }
    else {
        printf("Enter positive value");
    }
    
    return 0;
}

int fact (int n) {
    
    if(n == 1 || n==0) {
        return 1;
    }
    else {
        return n * fact(n-1);
    }
    
}

Output

Enter any number: 7
The Factorial is : 5040

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Programiz Quiz

Q. Which of the following statements is false?

Options:

1. A function that calls itself is called recursive function
2. Conditional statement prevents infinite recursive call
3. Recursive Function always return some value
4. None of the above

Answer: 3