Chapter 13.2, Problem 9SC

Program Plan Intro

Recursion:

• Java-recursion is a mechanism in which a method continuously calls itself.
• In java, a method which calls itself is called recursive method.
• Using this mechanism, some problems can be solved easily.
• For example, problems like, Tower of Hanoi(TOH), Inorder/Preorder/Postorder Tree Travels, DFS of Graph are solved using recursion.
• Syntax of recursive methods,

  //define recursive method

  returntype methodname()

  {

//code to be executed

//calling same method  

methodname();

}

• In the above code, a method “methodname()” is a recursive method because, in the definition, this method calls by itself.

Recursive helper method:

• The recursive helper method is used to identify how far the recursion has already proceeded or how far it still has to proceed.
• A task may often be solved by handing it over to a recursive helper method.
• The recursive helper method can be defined by slightly changing the original recursive method.