Direct and Indirect Recursion: Explained with Examples

Before starting this tutorial please read the previous tutorial first Concept of Recursion

Direct Recursion

When in the body of a method there is a call to the same method, we say that the method is directly recursive. That means Direct recursion occurs when a method invokes itself.

Indirect Recursion or mutually recursive

If method A calls method B, method B calls method C, and method C calls method A we call the methods A, B and C indirectly recursive or mutually recursive.

Indirect recursion occurs when a method invokes another method, eventually resulting in the original method being invoked again.

Chains of calls in indirect recursion can contain multiple methods, as well as branches, i.e. in the presence of one condition one method to be called, and provided a different condition another to be called.

The depth of indirection may vary.

Indirect recursion requires the same attention to base cases.

int num()
{
	...
	...
	int num();

}

int num()
{
	...
	...
	int sum();

}
int sum()
{
	...
	...
	int num();

}