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Recursion in C

Example

#include<stdio.h>  // Include the standard input-output library

// Function declaration
int factorial(int n);

int main() {
    // Variable declaration
    int num = 5;
    int result;

    // Function call
    result = factorial(num);

    // Print the result
    printf("Factorial of %d is %d\n", num, result);

    return 0;
}

// Function definition
int factorial(int n) {
    if (n == 0) {
        return 1;
    } else {
        return n * factorial(n - 1);
    }
}
        

Explanation:

Recursion in C is a process where a function calls itself directly or indirectly, allowing it to perform repeated tasks.

In this example:

• #include<stdio.h>: Includes the standard input-output library which allows us to use the printf function.
• int factorial(int n);: Declaration of the function factorial, which takes an integer argument and returns an integer.
• int main(): The main function where the program execution begins.
• result = factorial(num);: Calls the factorial function with argument 5, and stores the return value in the variable result.
• printf("Factorial of %d is %d\n", num, result);: Prints the result to the console.
• int factorial(int n): Definition of the factorial function.
• if (n == 0) { return 1; }: Base case that ends the recursion when n is 0.
• else { return n * factorial(n - 1); }: Recursive call that continues to calculate the factorial by calling itself with n - 1.
• return 0;: Ends the main function and returns 0 to the operating system, indicating that the program ended successfully.

In summary, recursion in C allows functions to call themselves to solve problems that can be broken down into smaller, similar sub-problems. The key to a recursive function is the base case, which stops the recursion, and the recursive case, which continues the process.