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Updated DoublyLinkedList.java

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Changes made in Insert and Delete functions.
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Pratham Gupta 2019-03-16 13:05:26 +05:30 committed by GitHub
parent 53b2b69988
commit ece940b655
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1 changed files with 18 additions and 6 deletions
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24
DataStructures/Lists/DoublyLinkedList.java
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@ -1,3 +1,4 @@
/** /**
* This class implements a DoublyLinkedList. This is done using the classes * This class implements a DoublyLinkedList. This is done using the classes
* LinkedList and Link. * LinkedList and Link.
@ -62,9 +63,15 @@ class DoublyLinkedList{
public void insertTail(int x){ public void insertTail(int x){
Link newLink = new Link(x); Link newLink = new Link(x);
newLink.next = null; // currentTail(tail) newlink --> newLink.next = null; // currentTail(tail) newlink -->
tail.next = newLink; // currentTail(tail) --> newLink --> if(isEmpty()) { // Check if there are no elements in list then it adds first element
newLink.previous = tail; // currentTail(tail) <--> newLink --> tail=newLink;
tail = newLink; // oldTail <--> newLink(tail) --> head=tail;
}
else {
tail.next = newLink; // currentTail(tail) --> newLink -->
newLink.previous = tail; // currentTail(tail) <--> newLink -->
tail = newLink; // oldTail <--> newLink(tail) -->
}
} }
/** /**
@ -72,12 +79,13 @@ class DoublyLinkedList{
* *
* @return The new head * @return The new head
*/ */
public void deleteHead(){ public Link deleteHead(){
Link temp = head; Link temp = head;
head = head.next; // oldHead <--> 2ndElement(head) head = head.next; // oldHead <--> 2ndElement(head)
head.previous = null; // oldHead --> 2ndElement(head) nothing pointing at old head so will be removed head.previous = null; // oldHead --> 2ndElement(head) nothing pointing at old head so will be removed
if(head == null) if(head == null)
tail = null; tail = null;
return temp;
} }
/** /**
@ -85,11 +93,15 @@ class DoublyLinkedList{
* *
* @return The new tail * @return The new tail
*/ */
public void deleteTail(){ public Link deleteTail(){
Link temp = tail; Link temp = tail;
tail = tail.previous; // 2ndLast(tail) <--> oldTail --> null tail = tail.previous; // 2ndLast(tail) <--> oldTail --> null
tail.next = null; // 2ndLast(tail) --> null tail.next = null; // 2ndLast(tail) --> null
if(tail==null)
{
head=null;
}
return temp;
} }
/** /**