344 lines
9.2 KiB
Java
344 lines
9.2 KiB
Java
package DataStructures.Lists;
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/**
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* This class implements a DoublyLinkedList. This is done using the classes
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* LinkedList and Link.
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* <p>
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* A linked list is similar to an array, it holds values. However,
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* links in a linked list do not have indexes. With a linked list
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* you do not need to predetermine it's size as it grows and shrinks
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* as it is edited. This is an example of a double ended, doubly
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* linked list. Each link references the next link and the previous
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* one.
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*
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* @author Unknown
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*/
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public class DoublyLinkedList {
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/**
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* Head refers to the front of the list
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*/
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private Link head;
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/**
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* Tail refers to the back of the list
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*/
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private Link tail;
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/**
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* Size refers to the number of elements present in the list
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*/
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private int size;
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/**
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* Default Constructor
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*/
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public DoublyLinkedList() {
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head = null;
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tail = null;
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size = 0;
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}
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/**
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* Constructs a list containing the elements of the array
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*
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* @param array the array whose elements are to be placed into this list
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* @throws NullPointerException if the specified collection is null
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*/
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public DoublyLinkedList(int[] array) {
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if (array == null) throw new NullPointerException();
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for (int i : array) {
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insertTail(i);
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}
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size = array.length;
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}
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/**
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* Insert an element at the head
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*
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* @param x Element to be inserted
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*/
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public void insertHead(int x) {
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Link newLink = new Link(x); // Create a new link with a value attached to it
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if (isEmpty()) // Set the first element added to be the tail
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tail = newLink;
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else
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head.previous = newLink; // newLink <-- currenthead(head)
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newLink.next = head; // newLink <--> currenthead(head)
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head = newLink; // newLink(head) <--> oldhead
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++size;
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}
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/**
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* Insert an element at the tail
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*
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* @param x Element to be inserted
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*/
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public void insertTail(int x) {
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Link newLink = new Link(x);
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newLink.next = null; // currentTail(tail) newlink -->
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if (isEmpty()) { // Check if there are no elements in list then it adds first element
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tail = newLink;
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head = tail;
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} else {
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tail.next = newLink; // currentTail(tail) --> newLink -->
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newLink.previous = tail; // currentTail(tail) <--> newLink -->
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tail = newLink; // oldTail <--> newLink(tail) -->
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}
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++size;
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}
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/**
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* Insert an element at the index
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*
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* @param x Element to be inserted
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* @param index Index(from start) at which the element x to be inserted
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*
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*/
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public void insertElementByIndex(int x,int index){
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if(index > size) throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);
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if(index == 0){
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insertHead(x);
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}else{
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if(index == size){
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insertTail(x);
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}else{
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Link newLink = new Link(x);
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Link previousLink = head; //
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for(int i = 1; i < index; i++){ //Loop to reach the index
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previousLink = previousLink.next;
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}
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// previousLink is the Link at index - 1 from start
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previousLink.next.previous = newLink;
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newLink.next = previousLink.next;
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newLink.previous = previousLink;
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previousLink.next = newLink;
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}
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}
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++size;
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}
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/**
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* Delete the element at the head
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*
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* @return The new head
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*/
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public Link deleteHead() {
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Link temp = head;
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head = head.next; // oldHead <--> 2ndElement(head)
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if (head == null) {
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tail = null;
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} else {
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head.previous = null; // oldHead --> 2ndElement(head) nothing pointing at old head so will be removed
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}
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--size;
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return temp;
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}
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/**
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* Delete the element at the tail
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*
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* @return The new tail
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*/
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public Link deleteTail() {
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Link temp = tail;
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tail = tail.previous; // 2ndLast(tail) <--> oldTail --> null
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if (tail == null) {
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head = null;
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} else{
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tail.next = null; // 2ndLast(tail) --> null
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}
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--size;
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return temp;
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}
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/**
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* Delete the element from somewhere in the list
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*
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* @param x element to be deleted
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* @return Link deleted
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*/
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public void delete(int x) {
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Link current = head;
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while (current.value != x) {// Find the position to delete
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if (current != tail) {
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current = current.next;
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} else {// If we reach the tail and the element is still not found
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throw new RuntimeException("The element to be deleted does not exist!");
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}
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}
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if (current == head)
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deleteHead();
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else if (current == tail)
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deleteTail();
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else { // Before: 1 <--> 2(current) <--> 3
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current.previous.next = current.next; // 1 --> 3
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current.next.previous = current.previous; // 1 <--> 3
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}
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--size;
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}
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/**
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* Inserts element and reorders
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*
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* @param x Element to be added
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*/
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public void insertOrdered(int x) {
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Link newLink = new Link(x);
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Link current = head;
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while (current != null && x > current.value) // Find the position to insert
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current = current.next;
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if (current == head)
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insertHead(x);
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else if (current == null)
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insertTail(x);
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else { // Before: 1 <--> 2(current) <--> 3
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newLink.previous = current.previous; // 1 <-- newLink
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current.previous.next = newLink; // 1 <--> newLink
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newLink.next = current; // 1 <--> newLink --> 2(current) <--> 3
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current.previous = newLink; // 1 <--> newLink <--> 2(current) <--> 3
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}
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++size;
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}
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/**
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* Deletes the passed node from the current list
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*
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* @param z Element to be deleted
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*/
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public void deleteNode(Link z) {
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if(z.next == null){
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deleteTail();
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} else if(z == head){
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deleteHead();
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} else{ //before <-- 1 <--> 2(z) <--> 3 -->
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z.previous.next = z.next; // 1 --> 3
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z.next.previous = z.previous; // 1 <--> 3
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}
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--size;
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}
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public static void removeDuplicates(DoublyLinkedList l ) {
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Link linkOne = l.head ;
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while(linkOne.next != null) { // list is present
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Link linkTwo = linkOne.next; // second link for comparison
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while(linkTwo.next!= null) {
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if(linkOne.value == linkTwo.value) // if there are duplicates values then
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l.delete(linkTwo.value); // delete the link
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linkTwo = linkTwo.next ; // go to next link
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}
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linkOne = linkOne.next; // go to link link to iterate the whole list again
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}
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}
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/**
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* Clears List
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*
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*/
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public void clearList(){
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head = null;
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tail = null;
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size = 0;
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}
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/**
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* Returns true if list is empty
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*
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* @return true if list is empty
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*/
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public boolean isEmpty() {
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return (head == null);
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}
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/**
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* Prints contents of the list
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*/
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public void display() { // Prints contents of the list
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Link current = head;
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while (current != null) {
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current.displayLink();
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current = current.next;
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}
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System.out.println();
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}
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}
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/**
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* This class is used to implement the nodes of the
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* linked list.
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*
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* @author Unknown
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*/
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class Link {
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/**
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* Value of node
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*/
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public int value;
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/**
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* This points to the link in front of the new link
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*/
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public Link next;
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/**
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* This points to the link behind the new link
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*/
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public Link previous;
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/**
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* Constructor
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*
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* @param value Value of node
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*/
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public Link(int value) {
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this.value = value;
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}
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/**
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* Displays the node
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*/
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public void displayLink() {
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System.out.print(value + " ");
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}
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/**
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* Main Method
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*
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* @param args Command line arguments
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*/
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public static void main(String args[]) {
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DoublyLinkedList myList = new DoublyLinkedList();
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myList.insertHead(13);
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myList.insertHead(7);
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myList.insertHead(10);
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myList.display(); // <-- 10(head) <--> 7 <--> 13(tail) -->
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myList.insertTail(11);
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myList.display(); // <-- 10(head) <--> 7 <--> 13 <--> 11(tail) -->
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myList.deleteTail();
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myList.display(); // <-- 10(head) <--> 7 <--> 13(tail) -->
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myList.delete(7);
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myList.display(); // <-- 10(head) <--> 13(tail) -->
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myList.insertOrdered(23);
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myList.insertOrdered(67);
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myList.insertOrdered(3);
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myList.display(); // <-- 3(head) <--> 10 <--> 13 <--> 23 <--> 67(tail) -->
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myList.insertElementByIndex(5, 1);
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myList.display(); // <-- 3(head) <--> 5 <--> 10 <--> 13 <--> 23 <--> 67(tail) -->
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myList.clearList();
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myList.display();
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myList.insertHead(20);
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myList.display();
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}
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}
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