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Updated DoublyLinkedList.java #718

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Merged
merged 2 commits into from
Mar 23, 2019
Merged

Updated DoublyLinkedList.java #718

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ece940b
Updated DoublyLinkedList.java
PrathamGupta Mar 16, 2019
1497487
Update DoublyLinkedList.java
yanglbme Mar 23, 2019
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Updated DoublyLinkedList.java 
Changes made in Insert and Delete functions.
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@PrathamGupta
PrathamGupta authored Mar 16, 2019
commit ece940b655a2af1992a8851d3ed2b694879c22ae
24 changes: 18 additions & 6 deletions DataStructures/Lists/DoublyLinkedList.java
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@

/**
* This class implements a DoublyLinkedList. This is done using the classes
* LinkedList and Link.
Expand Down Expand Up @@ -62,34 +63,45 @@ public void insertHead(int x){
public void insertTail(int x){
Link newLink = new Link(x);
newLink.next = null; // currentTail(tail) newlink -->
tail.next = newLink; // currentTail(tail) --> newLink -->
newLink.previous = tail; // currentTail(tail) <--> newLink -->
tail = newLink; // oldTail <--> newLink(tail) -->
if(isEmpty()) { // Check if there are no elements in list then it adds first element
tail=newLink;
head=tail;
}
else {
tail.next = newLink; // currentTail(tail) --> newLink -->
newLink.previous = tail; // currentTail(tail) <--> newLink -->
tail = newLink; // oldTail <--> newLink(tail) -->
}
}

/**
* Delete the element at the head
*
* @return The new head
*/
public void deleteHead(){
public Link deleteHead(){
Link temp = head;
head = head.next; // oldHead <--> 2ndElement(head)
head.previous = null; // oldHead --> 2ndElement(head) nothing pointing at old head so will be removed
if(head == null)
tail = null;
return temp;
}

/**
* Delete the element at the tail
*
* @return The new tail
*/
public void deleteTail(){
public Link deleteTail(){
Link temp = tail;
tail = tail.previous; // 2ndLast(tail) <--> oldTail --> null
tail.next = null; // 2ndLast(tail) --> null

if(tail==null)
{
head=null;
}
return temp;
}

/**
Expand Down