Created
June 6, 2015 20:28
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Queue using DLL
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| class Queue<T> { | |
| /* In Queue updates made at the both ends | |
| */ | |
| class Node { | |
| T data; | |
| Node prev; | |
| Node next; | |
| Node (T data) { | |
| this.data = data; | |
| this.next = null; | |
| this.prev = null; | |
| } | |
| } | |
| private Node front; | |
| private Node back; | |
| //Intialization | |
| Queue () { | |
| this.front = null; | |
| this.back = null; | |
| } | |
| //Add/Insert the data into a queue | |
| public void offer (T data) { | |
| Node tmp = new Node (data); | |
| if (this.front == null) { | |
| this.front = tmp; | |
| this.back = this.front; | |
| } else { | |
| tmp.next = this.front; | |
| this.front.prev = tmp; | |
| this.front = tmp; | |
| } | |
| } | |
| //Remove the data from a queue | |
| public T poll() { | |
| if (!isEmpty()) { | |
| Node tmp = this.back; | |
| T tmpData = (T)tmp.data; | |
| if (this.back == this.front) { | |
| this.back = null; | |
| this.front = null; | |
| } else { | |
| this.back = tmp.prev; | |
| tmp = null; | |
| } | |
| return tmpData ; | |
| } | |
| return null; | |
| } | |
| //Get the data from queue | |
| public T peek() { | |
| if (!isEmpty()) { | |
| T tmpData = (T) this.back.data; | |
| return tmpData; | |
| } | |
| return null; | |
| } | |
| public boolean isEmpty() { | |
| if (front == null && back == null) { | |
| return true; | |
| } | |
| return false; | |
| } | |
| public static void main(String[] args) { | |
| Queue<String> tQ = new Queue<String> (); | |
| tQ.offer("Hi"); | |
| tQ.offer("Hello"); | |
| tQ.offer("Bye"); | |
| System.out.println(tQ.peek()); | |
| tQ.poll(); | |
| System.out.println(tQ.peek()); | |
| tQ.poll(); | |
| System.out.println(tQ.peek()); | |
| tQ.poll(); | |
| System.out.println(tQ.peek()); | |
| tQ.offer("Bye"); | |
| System.out.println(tQ.peek()); | |
| } | |
| } |
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