Question
Write a method called removeEvens that removes the values in even-numbered indexes from a list, returning a new list that contains those values in their original order. For example, consider a variable list1 that stores the values [8, 13, 17, 4, 9, 12, 98, 41, 7, 23, 0, 92] and imagine that the following call is made:
LinkedIntList list2 = list1.removeEvens();
After the call, list1 should store [13, 4, 12, 41, 23, 92] and list2 should store [8, 17, 9, 98, 7, 0] . You may not call any methods of the class other than the constructor to solve this problem. You may not create any new nodes nor change the values stored in data fields to solve this problem. You must solve it by rearranging the links of the list.
Add the above method to the LinkedIntList class from this chapter.
Answer
Implementation of removeEvens method:
public LinkedIntList removeEvens()
{
LinkedIntList evensList = new LinkedIntList();
ListNode newCurrent = null;
ListNode previous = null;
int index = 0;
ListNode current = front;
while(current != null)
{
if(index % 2 == 0)
{
if(index == 0)
{
evensList.front = front;
front = front.next;
newCurrent = evensList.front;
previous = null;
current = front;
}
else
{
newCurrent.next = current;
newCurrent = newCurrent.next;
previous.next = current.next;
current = previous.next;
}
}
else
{
previous = current;
current = current.next;
}
index++;
}
if(newCurrent != null)
newCurrent.next = null;
return evensList;
}