Heapsort Implementation

clients/build.gradle

@@ -16,6 +16,7 @@ dependencies {
     implementation project(':module5')
     implementation project(':module6')
     implementation project(':module7')
+    implementation project(':module8')
     implementation project(':common')
     testImplementation project(':common')
 }

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

@@ -0,0 +1,23 @@
+package com.hithomelabs.clients.module8;
+
+import com.hithomelabs.princeton1.common.Apple;
+import com.hithomelabs.princeton1.module8.HeapSort;
+
+import java.util.Random;
+
+public class HeapSortClient {
+
+    public static void main(String[] args) {
+        int size = 10;
+        Apple[] apples = new Apple[size];
+        HeapSort<Apple> heap = new HeapSort<Apple>();
+
+        for (int i = 0; i < apples.length; i++) {
+            apples[i] = new Apple(new Random().nextInt(10));
+        }
+        heap.sort(apples);
+        for (int i = 0; i < apples.length; i++)
+            System.out.println(apples[i]);
+    }
+
+}

module8/build.gradle

@@ -0,0 +1,21 @@
+plugins {
+    id 'java'
+}
+
+group = 'com.hithomelabs.princeton1.module8'
+version = 'unspecified'
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    testImplementation platform('org.junit:junit-bom:5.10.0')
+    testImplementation 'org.junit.jupiter:junit-jupiter'
+    implementation project(':module5')
+    testImplementation project(':common')
+}
+
+test {
+    useJUnitPlatform()
+}

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

@@ -0,0 +1,52 @@
+package com.hithomelabs.princeton1.module8;
+
+/*
+ * * Designing Heap as a wrapper class with static methods that perform sink and swim operations on underlying comparable[] array
+ * * Heap does not have any instance variables, instance variables shall be housed by, the implementation using heaps, like priority queues and heap sort
+ */
+
+import com.hithomelabs.princeton1.module5.AbstractCustomSorts;
+
+public class Heap{
+
+    /*
+    * * Sink Node T with to it's appropriate place in a Heap of size N, if it's children exist and are greater
+    */
+    public static <T> void sink(T[] arr, int root, int N){
+        // *  Check if at least one child exists
+        while(2 * root <= N){
+            int j = 2 * root;
+        // *  Check if the right child exists and is larger than the left child, if yes swap right and left child
+            if(j+1 <= N){
+                if (less(arr[j], arr[j+1])) j++;
+            }
+            if (!less(arr[root], arr[j])) break;
+            exch(arr, root, j);
+        // * The root node has now sunken low, call sink recursively with new node to check if it sinks further
+            root = j;
+        }
+    }
+
+    // * * 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){
+        while(node > 1){
+            if(! less(arr[node/2],arr[node])) break;
+            exch(arr, node, node/2);
+            node = node/2;
+        }
+    }
+
+    private static <T> void exch(T[] arr, int i, int j){
+        T temp = arr[i];
+        arr[i] = arr[j];
+        arr[j] = temp;
+    }
+
+    private static <T> boolean less(T v, T w){
+
+        if(((Comparable<T>)v).compareTo(w) < 1 ) return true;
+        else return false;
+    }
+
+
+}

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

@@ -0,0 +1,31 @@
+package com.hithomelabs.princeton1.module8;
+
+import com.hithomelabs.princeton1.module5.AbstractCustomSorts;
+
+
+public class HeapSort<E> extends AbstractCustomSorts<E> {
+
+    @Override
+    public void sort(E[] arr) {
+        int N = arr.length;
+
+        E[] heapArr = (E[]) new Object[N+1];
+        // * * to simplify we copy original array from
+        System.arraycopy(arr, 0, heapArr, 1, N);
+
+        // * * An array of size N holds a heap of size N-1
+        coreSortingLogic(heapArr, N);
+        System.arraycopy(heapArr, 1, arr, 0, N);
+    }
+
+    private void coreSortingLogic(E[] arr, int N) {
+        // * * Converting array to max-heap an array in place
+        for (int i = N/2; i >= 1; i--)
+            Heap.sink(arr, i, N);
+        // * * After converting to max-heap, in every iteration remove the max element of the heap
+        while(N > 1){
+            exch(arr, 1, N--);
+            Heap.sink(arr, 1, N);
+        }
+    }
+}

module8/src/test/java/com/hithomelabs/princeton1/module8/HeapSortTest.java

@@ -0,0 +1,51 @@
+package com.hithomelabs.princeton1.module8;
+
+import com.hithomelabs.princeton1.common.Apple;
+import org.junit.jupiter.api.*;
+
+import java.util.ArrayList;
+import java.util.Random;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class HeapSortTest {
+
+    private HeapSort<Apple> heap;
+    private ArrayList<Apple> apples;
+    private Random random;
+
+    @BeforeEach
+    void setUp() {
+        heap = new HeapSort<Apple>();
+        apples = new ArrayList<Apple>();
+        random = new Random();
+    }
+
+    @Test
+    @DisplayName("Sort a heap of a 100 random sized apples")
+    public void testSort(){
+        for(int i = 0; i < 100; i++)
+            apples.add(new Apple(random.nextInt(1000)));
+        Apple[] arr = apples.toArray(new Apple[apples.size()]);
+        heap.sort(arr);
+        apples.sort(null);
+        Apple[] sorted =  apples.toArray(new Apple[apples.size()]);
+        Assertions.assertArrayEquals(sorted, arr);
+    }
+
+    @Test
+    @DisplayName("Sort 100 apples in descending order")
+    public void testSortBorder(){
+        for(int i = 0; i < 100; i++)
+            apples.add(new Apple(100 - i));
+        Apple[] arr = apples.toArray(new Apple[apples.size()]);
+        heap.sort(arr);
+        apples.sort(null);
+        Apple[] sorted =  apples.toArray(new Apple[apples.size()]);
+        Assertions.assertArrayEquals(sorted, arr);
+    }
+
+    @AfterEach
+    void tearDown() {
+    }
+}

settings.gradle

@@ -17,4 +17,5 @@ include 'module5'
 include 'module6'
 include 'common'
 include 'module7'
+include 'module8'