Question

In JAVA Recursive Methods

For exercises 16 to 18 assume we have a sorted linked list of Integer. The start of the linked list is referenced by values which, of course, is of type LLNode. For example purposes, assume values points to a list containing 3, 6, 6, 9, 12, 15, 18, 19, 19, and 20. You can and should assume the list in question is sorted in nondecreasing order. For each of these exercises you should also create a driver application that demonstrates that your new method operates correctly.

16. Write a recursive method numEvens(LLNode list) that returns how many even numbers are contained in list. For our example list numEvens(values) would return 5 (the even numbers are 6, 6, 12, 18, and 20).

17. Write a recursive method contains(int target, LLNode list) that returns true if list contains target and false otherwise. For our example list contains(15, values) would return true while contains(10, values) would return false.

18. Write a recursive method remove(int target, LLNode list) that removes all occurrences of target from list and returns a reference to the new list. For our example list the statement values = remove(6, values); would result in values referencing the list containing 3 9 12 15 18 19 19 and 20. If target is not contained in list then the list remains unchanged.

Comments are always hepful

Answer 1

A.

int numEvens(llNode list)
{
   if(list==null)
       return 0;
   return (list.data%2==0 ? 1 : 0) + numEvens(list.next);
}

B.

boolean contains(int target, llNode list)
{
   if(list==null || list.data > target)
       return false;
  
   if(list.data==target)
       return true;
   else
       return contains(target, list.next);
}

C.

llNode remove(int target, llNode list)
{
   if(list==null || list.data > target)
       return list;
   if(list.data==target)
       return remove(target, list.next);
   else
   {
       list.next=remove(target, list.next);
       return list;
   }
}