Merge pull request tarunsinghofficial#1797 from Aryanshaw/main

Queue implementation in java

Java_Programs_for_beginners/Queue/Deque.java

@@ -0,0 +1,16 @@
+package Ds.Queue;
+import java.util.*;
+public class Deque {
+
+ public static void main(String[] args) {
+ ArrayDeque<Integer> dq = new ArrayDeque();
+ dq.addFirst(12);
+ dq.addFirst(23);
+ dq.addFirst(42);
+ dq.pop();
+
+ System.out.println(dq.peek());
+
+ }
+
+}

Java_Programs_for_beginners/Queue/Runner.java

@@ -0,0 +1,20 @@
+package Ds.Queue;
+
+public class Runner {
+
+ public static void main(String[] args) {
+ arrayQueue q = new arrayQueue();
+ q.enQueue(5);
+ q.enQueue(4);
+ q.enQueue(3);
+ q.enQueue(7);
+ q.enQueue(6);
+ q.enQueue(1);
+// q.enQueue(0);
+
+ q.deQueue();
+ q.show();
+ System.out.println("size is "+ q.getSize());
+ }
+
+}

Java_Programs_for_beginners/Queue/arrayQueue.java

@@ -0,0 +1,50 @@
+package Ds.Queue;
+
+public class arrayQueue {
+
+ int queue[] = new int [5];
+ int size;
+ int front;
+ int back;
+
+ public void enQueue(int data) {
+ if(!isFull()) {
+ queue[back] = data;
+ back = (back +1)%5;
+ size++;
+ }else {
+ System.out.println("Queue is full"); 
+ }
+ }
+ public int deQueue() {
+ int data = queue[front];
+ if(isEmpty()) {
+ front= (front + 1)%5;
+ size--;
+ }else {
+ System.out.println("queue is empty");
+ }
+ return data;
+ }
+
+ public void show() {
+ System.out.println("The number of elements are: ");
+ for(int i=0; i < size; i++) {
+ System.out.println(queue[(front+ i)%5]+ " ");
+ } 
+ }
+ public int getSize() { 
+ return size;
+ }
+ public boolean isEmpty() {
+ return getSize()==0;
+ }
+ public boolean isFull() {
+ return getSize()==5;
+ }
+ public static void main(String[] args) {
+
+
+ }
+
+}

Java_Programs_for_beginners/Queue/myDeque.java

@@ -0,0 +1,44 @@
+package Ds.Queue;
+
+public class myDeque<E> {
+ Node head , tail;
+ public void addHead(E data) {
+ Node <E> toAdd = new Node(data);
+ if(head==null) {
+ head = tail = toAdd;
+ return;
+ }
+ head.next = toAdd;
+ toAdd.previous = head;
+ toAdd= head;
+
+ }
+ public E removeLast() {
+ if(head==null) {
+ return null;
+ }
+ Node<E> toRemove = tail;
+ tail = tail.next;
+ tail.previous = null;
+
+ if(tail == null) {
+ head = null;
+ }
+ return toRemove.data;
+ }
+
+ public static class Node<E>{
+ E data;
+ Node next , previous;
+
+ public Node(E data) {
+ this.data = data;
+ this.next = this.previous = null;
+ }
+ }
+ public static void main(String[] args) {
+ // TODO Auto-generated method stub
+
+ }
+
+}

Java_Programs_for_beginners/Queue/priorityQueue.java

@@ -0,0 +1,50 @@
+package Ds.Queue;
+
+import java.util.*;
+
+public class priorityQueue {
+
+ public static void main(String[] args) {
+// PriorityQueue <String> pq = new PriorityQueue();
+// pq.add("orange");
+// pq.add("apple");
+// pq.add("hulalal");
+// pq.add("hikli");
+// pq.add("babul");
+// 
+// System.out.println(pq);
+// System.out.println(pq.remove());
+// System.out.println(pq.remove());
+// System.out.println(pq.remove());
+// 
+ Scanner sc = new Scanner(System.in);
+ int t = sc.nextInt();
+ while(t-- !=0) {
+ int n = sc.nextInt();
+ int k = sc.nextInt();
+ int a[] = new int [n];
+ for(int i = 0;i<n ; i++) {
+ a[i] = sc.nextInt();
+ }
+ PriorityQueue <Integer> pq = new PriorityQueue();
+ for(int i = 0;i<n ; i++) {
+ if(i<k) {
+ pq.add(a[i]);
+ }else {
+ if(pq.peek() < a[i]) {
+ pq.poll();
+ pq.add(a[i]);
+ }
+ }
+ }
+ ArrayList <Integer> ans = new ArrayList(pq);
+ Collections.sort(ans , Collections.reverseOrder());
+
+ for(int x: ans) {
+ System.out.print(x+" ");
+ }
+ System.out.println();
+ }
+ }
+
+}

Java_Programs_for_beginners/Queue/queue.java

@@ -0,0 +1,76 @@
+package Ds.Queue;
+
+import java.lang.reflect.Array;
+import java.util.ArrayList;
+
+public class queue {
+ private static final int n = 20;
+
+ int [] arr;
+ int front;
+ int back;
+ int size;
+
+ public queue () {
+ arr = new int [n]; 
+ front = -1;
+ back = -1;
+ }
+
+ void push(int x) {
+ if(back == n-1) {
+ System.out.println("Queue overflow");
+ return;
+ }
+ back++;
+ arr[back]= x;
+ size++;
+
+ if(front == -1) {
+ front++;
+ }
+ }
+ void pop() {
+ if(front == -1 || front> back) {
+ System.out.println("No elements in queue");
+ return;
+ }
+ size--;
+ front++;
+
+ }
+ public void show() {
+ System.out.println("The number of elements are: ");
+ for(int i=0; i < size; i++) {
+ System.out.println(arr[front+ i]+ " ");
+ }
+ }
+ int peek() {
+ if(front == -1 || front> back) {
+ System.out.println("No elements in queue");
+ return -1;
+ }
+ return arr[front];
+ }
+ boolean empty() {
+ if(front == -1 || front> back) {
+ return true;
+ }
+ return false;
+ }
+ public static void main (String [] args) {
+ queue q = new queue();
+ q.push(1);
+ q.push(2);
+ q.push(3);
+ q.push(4);
+
+ q.pop();
+ q.show();
+// System.out.println(q.peek());
+// q.pop();
+ } 
+
+
+
+}

Java_Programs_for_beginners/Queue/queueLL.java

@@ -0,0 +1,31 @@
+package Ds.Queue;
+
+import java.util.*;
+
+import Ds.LinkedList.MyLinkedList.Node;
+
+public class queueLL<E> {
+
+ private Node<E> head, rear;
+ public void enqueue(E e) {
+ Node<E> toAdd = new Node(e);
+ if(head==null) {
+ head=rear= toAdd;
+ return;
+ } 
+ rear.next = toAdd;
+ rear = rear.next;
+ }
+ public E dequeue(E e) {
+ if(head==null) {
+ return null;
+ }
+ Node<E> temp = head;
+ head= head.next;
+ if(head==null) {
+ rear = null;
+ }
+ return temp.data;
+
+ }
+}

Java_Programs_for_beginners/Queue/queueStack.java

@@ -0,0 +1,51 @@
+package Ds.Queue;
+
+import java.util.Stack;
+
+public class queueStack {
+
+// public class que{
+ Stack<Integer> s1 = new Stack();
+ Stack<Integer> s2 = new Stack();
+
+ public void push(int x) {
+ s1.push(x);
+ }
+ public int pop() {
+ if(s1.empty() && s2.empty()) {
+ System.out.println("Queue is empty");
+ return -1;
+ }
+ if(s2.empty()) {
+ while(!s1.empty()) {
+ s2.push(s1.peek());
+ s1.pop();
+ }
+ }
+ int top = s2.peek();
+ s2.pop();
+ return top;
+ }
+ boolean isEmpty() {
+ if(s1.empty() && s2.empty()) {
+ return true;
+ }
+ return false;
+ }
+// };
+ public static void main(String[] args) {
+ queueStack q = new queueStack();
+// que i = new que();
+ q.push(1);
+ q.push(2);
+ q.push(3);
+ q.push(4);
+
+ System.out.println(q.pop());
+ System.out.println(q.pop()); 
+ System.out.println(q.pop()); 
+ System.out.println(q.pop());
+
+ System.out.println(q.pop()); 
+ }
+}