Chapter 13, Problem 1RE

Explanation of Solution

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.

Iteration:

• Iteration is a mechanism to sequence through a block of code repeatedly until a condition meets.
• The iteration mechanism uses the loops to solve the problem. The loops can be either “for”, “while” and “do..while”.
• Common example of problems that uses iteration are, iterating through a list of grades to find the average of grade points, processing the text file and so on.

Infinite recursion:

• The infinite recursion occurs when the recursion never stops.
• In this case, a method calls itself over and over again and never reaches an end.
• Infinite recursion occurs when the recursive method fails to stop recursion. The infinite recursion shows bug’s in the program.

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.
• The recursive helper method is also recursive and usually called by a non-recursive method.