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
int sum(int n);
int number, result;
printf("Enter a positive integer: ");
result = sum(number);
int sum(int n)
return n + sum(n-1); // sum() function calls itself
Enter a positive integer:
Initially, the sum() is called from the main() function with number passed as an argument.
Suppose, the value of n is 3 initially. During next function call, 2 is passed to the sum() function. In next function call, 1 is passed to the function. This process continues until n is equal to 0.
When n is equal to 0, there is no recursive call and the sum of integers is returned to the main() function.
Advantages and Disadvantages of Recursion
Recursion makes program elegant and cleaner. All algorithms can be defined recursively which makes it easier to visualize and prove.
If the speed of the program is vital then, you should avoid using recursion. Recursions use more memory and are generally slow.