C Recursion

Syntax

Recursion is a technique in programming where a function calls itself repeatedly to perform a particular task. The syntax for a recursive function in C is:

data_type recursive_function_name(arguments) {
    // base case, return a value
    if (some condition) {
        return some_value;
    }
    // recursive case, call the function again
    recursive_function_name(arguments);
    // process results
    // return a value
}

Example

To help illustrate the concept of recursion, here is an example of a recursive function that calculates the factorial of a number:

#include <stdio.h>

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

int main() {
    int n = 5;
    int result = factorial(n);
    printf("%d! = %d\n", n, result);
    return 0;
}

Output

5! = 120

Explanation

In the above example, the factorial() function is called recursively to calculate the factorial of a number. The base case for this function is when the input number n is equal to 0, and the function returns 1. For any input number greater than zero, the function calls itself with n-1 as the argument and multiplies the result with n. When the base case is reached, the function returns the final result.

Use

Recursion can be used in a variety of ways in C programming, including:

• Traversing hierarchical data structures such as binary trees or linked lists
• Implementing searching algorithms such as binary search
• Generating permutations and combinations of elements

Important Points

• Recursion can lead to stack overflow if not implemented properly, so it is important to have a base case that will eventually be reached to stop the recursion.
• A recursive function should not call itself indefinitely to prevent an infinite loop.
• Recursion can be an elegant solution to some problems, but it may not always be the most efficient solution.

Summary

Recursion is a powerful technique in programming where a function calls itself repeatedly until a base case is reached. A recursive function can be used to solve a variety of problems, such as calculating factorials or traversing data structures. However, it is important to implement recursion properly with a clear base case to prevent stack overflow and infinite loops.