priority queue implementation added (#20)

Reviewed-on: Hithomelabs/Princeton1#20
Reviewed-by: hitanshu <hitanshu98@gmail.com>
Co-authored-by: Kruti Shah <krutis0201@gmail.com>
Co-committed-by: Kruti Shah <krutis0201@gmail.com>

clients/src/main/java/com/hithomelabs/clients/module8/PriorityQueueClient.java

@@ -0,0 +1,18 @@
+package com.hithomelabs.clients.module8;
+
+import com.hithomelabs.princeton1.common.Apple;
+import com.hithomelabs.princeton1.module8.PriorityQueue;
+
+import java.util.Random;
+
+public class PriorityQueueClient {
+    public static void main(String[] args){
+        PriorityQueue<Apple> priorityQueue = new PriorityQueue<>();
+        for(int i=0; i<100; i++){
+            priorityQueue.enqueue(new Apple(new Random().nextInt(100)));
+        }
+        while (!priorityQueue.isEmpty()){
+            System.out.println(priorityQueue.dequeue());
+        }
+    }
+}

module8/build.gradle

@@ -13,6 +13,7 @@ dependencies {
     testImplementation platform('org.junit:junit-bom:5.10.0')
     testImplementation 'org.junit.jupiter:junit-jupiter'
     implementation project(':module5')
+    implementation project(':module4')
     testImplementation project(':common')
 }
 

module8/src/main/java/com/hithomelabs/princeton1/module8/Heap.java

@@ -32,7 +32,7 @@ public class Heap implements MeasurableHelper {
     }
 
     // * * Swim if element is not root, and parent is lesser than node
-    public static <T extends Comparable<T>> void swim(T[] arr, int node, int N, Comparator<T> cmp, SortingMetaData metaData){
+    public static <T> void swim(T[] arr, int node, int N, Comparator<T> cmp, SortingMetaData metaData){
         while(node > 1){
             if(! MeasurableHelper.less(arr[node/2],arr[node], cmp, metaData)) break;
             MeasurableHelper.exch(arr, node, node/2, metaData);

module8/src/main/java/com/hithomelabs/princeton1/module8/PriorityQueue.java

@@ -0,0 +1,66 @@
+package com.hithomelabs.princeton1.module8;
+
+import com.hithomelabs.princeton1.module4.Queue;
+import com.hithomelabs.princeton1.module5.ComparableHelper;
+
+import java.util.Iterator;
+
+public class PriorityQueue<E> extends Queue<E> implements ComparableHelper {
+    private int size;
+    private E[] arr;
+    private static final int CAPACITY = 100;
+    private int capacity;
+
+    public PriorityQueue(){
+        this(CAPACITY);
+    }
+
+    public PriorityQueue(int capacity){
+        arr = (E[]) new Object[capacity+1];
+        this.capacity = capacity;
+    }
+
+    @Override
+    public boolean isEmpty() {
+        return size == 0;
+    }
+
+    @Override
+    public E dequeue() {
+        if(isEmpty())
+            return null;
+        E value = arr[1];
+        ComparableHelper.exch(arr, 1, size);
+        arr[size--] = null;
+        Heap.sink(arr, 1, size, null, null);
+        return value;
+    }
+
+    @Override
+    public void enqueue(E element) {
+        arr[++size] = element;
+        Heap.swim(arr, size, size, null, null);
+    }
+
+    @Override
+    public int size() {
+        return size;
+    }
+
+    @Override
+    public Iterator iterator() {
+        return new Iterator() {
+
+            int index = 1;
+            @Override
+            public boolean hasNext() {
+                return index <= size;
+            }
+
+            @Override
+            public Object next() {
+                return arr[index++];
+            }
+        };
+    }
+}