# C Recursion ## C Recursion

C Recursion: In this tutorial, you will learn to write recursive functions in C programming with the help of an example.

A function that calls itself is known as a recursive function. What’s more, this method is known as recursion.

## How recursion works?

```void recurse()
{
... .. ...
recurse();
... .. ...
}

int main()
{
... .. ...
recurse();
... .. ...
}``` The recursion continues until some condition is met to prevent it.To prevent infinite recursion, if…else statement (or similar approach) can be used where one branch makes the recursive call, and others don’t.

Example: Sum of Natural Numbers Using 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:3
sum = 6```

Initially, the sum() is called from the main() function with the number passed as an argument.

Suppose, the value of n inside sum() is 3 initially. During the next function call, 2 is passed to the sum() function. This process continues until n is equal to 0.

When n is equal to 0, the if condition fails and the else part is executed returning the sum of integers ultimately to the main() function.

Recursion makes the program exquisite. In any case, if the execution is crucial, use circles rather as recursion are normally much slower.

That being stated, recursion is a significant idea. It is as often as possible used in data structure and algorithms. For instance, it is entirely expected to utilize recursion in issues, for example, tree traversal.

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