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Merge pull request #718 from PrathamGupta/patch-1

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Updated DoublyLinkedList.java
This commit is contained in:
Libin Yang
2019-03-23 15:44:04 +08:00
committed by GitHub
parent cd60c39b76 14974872fd
commit 45757c0165
1 changed files with 201 additions and 183 deletions
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378
DataStructures/Lists/DoublyLinkedList.java
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@ -1,166 +1,180 @@
/** /**
* 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.
* * <p>
* A linked list is simplar to an array, it holds values. However, * A linked list is similar to an array, it holds values. However,
* links in a linked list do not have indees. With a linked list * links in a linked list do not have indexes. With a linked list
* you do not need to predetermine it's size as it grows and shrinks * you do not need to predetermine it's size as it grows and shrinks
* as it is edited. This is an example of a double ended, doubly * as it is edited. This is an example of a double ended, doubly
* linked list. Each link references the next link and the previous * linked list. Each link references the next link and the previous
* one. * one.
* *
* @author Unknown * @author Unknown
*
*/ */
class DoublyLinkedList{ class DoublyLinkedList {
/** Head refers to the front of the list */ /**
private Link head; * Head refers to the front of the list
/** Tail refers to the back of the list */ */
private Link tail; private Link head;
/**
* Tail refers to the back of the list
*/
private Link tail;
/** /**
* Default Constructor * Default Constructor
*/ */
public DoublyLinkedList(){ public DoublyLinkedList() {
head = null; head = null;
tail = null; tail = null;
} }
/** /**
* Constructs a list containing the elements of the array * Constructs a list containing the elements of the array
* @param array the array whose elements are to be placed into this list *
* @throws NullPointerException if the specified collection is null * @param array the array whose elements are to be placed into this list
*/ * @throws NullPointerException if the specified collection is null
public DoublyLinkedList(int[] array){ */
if (array == null) throw new NullPointerException(); public DoublyLinkedList(int[] array) {
for (int i:array) { if (array == null) throw new NullPointerException();
insertTail(i); for (int i : array) {
} insertTail(i);
} }
}
/** /**
* Insert an element at the head * Insert an element at the head
* *
* @param x Element to be inserted * @param x Element to be inserted
*/ */
public void insertHead(int x){ public void insertHead(int x) {
Link newLink = new Link(x); //Create a new link with a value attached to it Link newLink = new Link(x); // Create a new link with a value attached to it
if(isEmpty()) //Set the first element added to be the tail if (isEmpty()) // Set the first element added to be the tail
tail = newLink; tail = newLink;
else else
head.previous = newLink; // newLink <-- currenthead(head) head.previous = newLink; // newLink <-- currenthead(head)
newLink.next = head; // newLink <--> currenthead(head) newLink.next = head; // newLink <--> currenthead(head)
head = newLink; // newLink(head) <--> oldhead head = newLink; // newLink(head) <--> oldhead
} }
/** /**
* Insert an element at the tail * Insert an element at the tail
* *
* @param x Element to be inserted * @param x Element to be inserted
*/ */
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) -->
}
}
/** /**
* Delete the element at the head * Delete the element at the head
* *
* @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;
}
/** /**
* Delete the element at the tail * Delete the element at the tail
* *
* @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;
}
} /**
* Delete the element from somewhere in the list
*
* @param x element to be deleted
* @return Link deleted
*/
public void delete(int x) {
Link current = head;
/** while (current.value != x) // Find the position to delete
* Delete the element from somewhere in the list current = current.next;
*
* @param x element to be deleted
* @return Link deleted
*/
public void delete(int x){
Link current = head;
while(current.value != x) //Find the position to delete if (current == head)
current = current.next; deleteHead();
if(current == head) else if (current == tail)
deleteHead(); deleteTail();
else if(current == tail) else { // Before: 1 <--> 2(current) <--> 3
deleteTail(); current.previous.next = current.next; // 1 --> 3
current.next.previous = current.previous; // 1 <--> 3
}
}
else{ //Before: 1 <--> 2(current) <--> 3 /**
current.previous.next = current.next; // 1 --> 3 * Inserts element and reorders
current.next.previous = current.previous; // 1 <--> 3 *
} * @param x Element to be added
} */
public void insertOrdered(int x) {
Link newLink = new Link(x);
Link current = head;
while (current != null && x > current.value) // Find the position to insert
current = current.next;
/** if (current == head)
* Inserts element and reorders insertHead(x);
*
* @param x Element to be added
*/
public void insertOrdered(int x){
Link newLink = new Link(x);
Link current = head;
while(current != null && x > current.value) //Find the position to insert
current = current.next;
if(current == head) else if (current == null)
insertHead(x); insertTail(x);
else if(current == null) else { // Before: 1 <--> 2(current) <--> 3
insertTail(x); newLink.previous = current.previous; // 1 <-- newLink
current.previous.next = newLink; // 1 <--> newLink
newLink.next = current; // 1 <--> newLink --> 2(current) <--> 3
current.previous = newLink; // 1 <--> newLink <--> 2(current) <--> 3
}
}
else{ //Before: 1 <--> 2(current) <--> 3 /**
newLink.previous = current.previous; // 1 <-- newLink * Returns true if list is empty
current.previous.next = newLink; // 1 <--> newLink *
newLink.next = current; // 1 <--> newLink --> 2(current) <--> 3 * @return true if list is empty
current.previous = newLink; // 1 <--> newLink <--> 2(current) <--> 3 */
} public boolean isEmpty() {
} return (head == null);
}
/** /**
* Returns true if list is empty * Prints contents of the list
* */
* @return true if list is empty public void display() { // Prints contents of the list
*/ Link current = head;
public boolean isEmpty(){ while (current != null) {
return(head == null); current.displayLink();
} current = current.next;
}
/** System.out.println();
* Prints contents of the list }
*/
public void display(){ //Prints contents of the list
Link current = head;
while(current!=null){
current.displayLink();
current = current.next;
}
System.out.println();
}
} }
/** /**
@ -168,57 +182,61 @@ class DoublyLinkedList{
* linked list. * linked list.
* *
* @author Unknown * @author Unknown
*
*/ */
class Link{ class Link {
/** Value of node */ /**
public int value; * Value of node
/** This points to the link in front of the new link */ */
public Link next; public int value;
/** This points to the link behind the new link */ /**
public Link previous; * This points to the link in front of the new link
*/
public Link next;
/**
* This points to the link behind the new link
*/
public Link previous;
/** /**
* Constructor * Constructor
* *
* @param value Value of node * @param value Value of node
*/ */
public Link(int value){ public Link(int value) {
this.value = value; this.value = value;
} }
/** /**
* Displays the node * Displays the node
*/ */
public void displayLink(){ public void displayLink() {
System.out.print(value+" "); System.out.print(value + " ");
} }
/** /**
* Main Method * Main Method
* *
* @param args Command line arguments * @param args Command line arguments
*/ */
public static void main(String args[]){ public static void main(String args[]) {
DoublyLinkedList myList = new DoublyLinkedList(); DoublyLinkedList myList = new DoublyLinkedList();
myList.insertHead(13);
myList.insertHead(7);
myList.insertHead(10);
myList.display(); // <-- 10(head) <--> 7 <--> 13(tail) -->
myList.insertHead(13); myList.insertTail(11);
myList.insertHead(7); myList.display(); // <-- 10(head) <--> 7 <--> 13 <--> 11(tail) -->
myList.insertHead(10);
myList.display(); // <-- 10(head) <--> 7 <--> 13(tail) -->
myList.insertTail(11); myList.deleteTail();
myList.display(); // <-- 10(head) <--> 7 <--> 13 <--> 11(tail) --> myList.display(); // <-- 10(head) <--> 7 <--> 13(tail) -->
myList.deleteTail(); myList.delete(7);
myList.display(); // <-- 10(head) <--> 7 <--> 13(tail) --> myList.display(); // <-- 10(head) <--> 13(tail) -->
myList.delete(7); myList.insertOrdered(23);
myList.display(); // <-- 10(head) <--> 13(tail) --> myList.insertOrdered(67);
myList.insertOrdered(3);
myList.insertOrdered(23); myList.display(); // <-- 3(head) <--> 10 <--> 13 <--> 23 <--> 67(tail) -->
myList.insertOrdered(67); }
myList.insertOrdered(3);
myList.display(); // <-- 3(head) <--> 10 <--> 13 <--> 23 <--> 67(tail) -->
}
} }