C Recursion
A function that calls itself is known as arecursive function. And, this technique is known as recursion.
How it works?
void recurse(){
... .. ...
resurse();
... .. ...
}
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 other doesn't.
Example : Sum of Natural Numbers Using Recursion
#include<studio.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 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, the if condition fails and the else part is executed returning the sum of n is equal to 0.
When n is equal to 0, if condition fails and the else part is executed returning to the main()
function.
Advantages and disadvantages of Recursion.
Recursion makes program elegant. However, if performance is vital , use loop instead as recursion is usually much slower.
That being said, recursion is an important concept. It is frequently used in data structures and algorithms .
For instance, it is common to use resursion in problems such as tree traversal.
