Removing extends and simplifying life

.gitignore

@@ -1,6 +1,7 @@
 # Ignore Gradle project-specific cache directory
 .gradle
-
+# Igonre the .idea directory
+.idea
 # Ignore Gradle build output directory
 build
 bin

module4/src/main/java/com/hithomelabs/princeton1/module4/ArrayQueue.java

@@ -5,100 +5,28 @@ import java.util.Iterator;
 import javax.annotation.Nonnull;
 
 public class ArrayQueue<E> extends Queue<E>{
-
-    // insertion from tail, removal from head
-    public static final int DEFAULT_CAPACITY = 10;
-    private int capacity;
-    private int tail;
-    private int head;
-    private int size;
-    private E[] arr;
-
-    public ArrayQueue(){
-        this(DEFAULT_CAPACITY);
-    }
-
-    public ArrayQueue(int capacity){
-        this.capacity = capacity;
-        arr = (E[]) new Object[this.capacity];
-        size = 0;
-    }
-
     @Override
     public boolean isEmpty() {
-        return size == 0;
+        return false;
     }
 
     @Override
     public E dequeue() {
-        if(isEmpty())
-            return null;
-        else{
-            E element = arr[head];
-            // Garbage collection
-            arr[head] = null;
-            head = (head+1)%capacity;
-            size = size - 1;
-            if(capacity >= 40 && size < capacity/4){
-                capacity = capacity/2;
-                resize(capacity, capacity*2);
-            }
-            return element;
-        }
+        return null;
     }
 
     @Override
     public void enqueue(E element) {
-        // We plan capacity expansion if needed
-        if (size == capacity){
-            capacity = capacity * 2;
-            resize(capacity, capacity/2);
-        }
-        arr[tail] = element;
-        tail = (tail + 1) % capacity;
-        ++size;
-    }
-
-    // When resize takes place always the original array is full, so copy the complete array as is
-    private void resize(int capacity, int oldCapacity) {
-        E[] resizedArr = (E[]) new Object[capacity];
-        for(int i = 0; i < size; i++) {
-            resizedArr[i] = arr[head];
-            // halving because capacity has now doubled
-            arr[head] = null;
-            head = (head + 1) % oldCapacity;
-        }
-        arr = resizedArr;
-        // When resizing takes place, we bring the head to 0 and the tail to size
-        // tail is where new inserts will be made and head will be where elements will be removed
-        tail = size;
-        head = 0;
 
     }
 
     @Override
     public int size() {
-        return size;
+        return 0;
     }
 
     @Override
-    @Nonnull
     public Iterator<E> iterator() {
-        return new Iterator<E>() {
-            int counter = size;
-            int pointer = head;
-            @Override
-            public boolean hasNext() {
-                return counter != 0;
-            }
-
-            @Override
-            public E next() {
-                E element = arr[pointer];
-                pointer = (pointer + 1)% capacity;
-                --counter;
-                return element;
-            }
-        };
+        return null;
     }
 }

module4/src/main/java/com/hithomelabs/princeton1/module4/ArrayStack.java

@@ -5,94 +5,28 @@ import javax.annotation.Nonnull;
 // Concrete implementation of stack using arrays
 // Creating a generic stack of type E
 public class ArrayStack<E> extends Stack<E> {
-
-    // Capacity and size are two variables, capacity determines total capacity of array, capacity defaults at 10
-    // every time size == capacity, capacity = 2 * capacity
-    private static final int DEFAULT_CAPACITY = 10;
-    private int capacity;
-    private int size;
-    private E[] arr;
-
-    public ArrayStack(int capacity){
-        this.capacity = capacity;
-        arr = (E[]) new Object[this.capacity];
-    }
-
-    // Constructor chaining, default constructor will call parametrized constructor with default initial capacity 10
-    public ArrayStack(){
-        this(DEFAULT_CAPACITY);
-    }
-
     @Override
     public boolean isEmpty() {
-        return size == 0;
+        return false;
     }
 
-    private void changeCapacity(int newCapacity){
-        E[] resizedArr = (E[]) new Object[newCapacity];
-        for (int i = 0; i < size; i++)
-            resizedArr[i] = arr[i];
-        arr = resizedArr;
-    }
-
-    private void incrementSize(){
-        if (size == capacity){
-            capacity = 2 * capacity;
-            changeCapacity(capacity);
-        }
-    }
-
-    // Push always happens at the end of the stack
-    // Say the size of the stack is 1, new element gets inserted  at 1
     @Override
     public void push(E element) {
-        // Lazy approach, we assume size to always be lesser than capacity
-        incrementSize();
-        arr[size++] = element;
+
     }
 
     @Override
     public E pop() {
-        if (isEmpty())
-            return null;
-        else{
-            E e = arr[--size];
-            arr[size] = null;
-            checkResize();
-            return e;
-        }
-    }
-
-    private void checkResize() {
-        if (size < capacity / 4 && capacity >= 20){
-            capacity = capacity / 2;
-            changeCapacity(capacity);
-        }
+        return null;
     }
 
     @Override
     public int size() {
-        return size;
+        return 0;
     }
 
     @Override
-    @Nonnull
     public Iterator<E> iterator() {
-        return new Iterator<E>() {
-
-            int current = 0;
-
-            @Override
-            public boolean hasNext() {
-                return current != size;
-            }
-
-            @Override
-            public E next() {
-                E element = arr[current];
-                current = current + 1;
-                return element;
-            }
-        };
+        return null;
     }
 }

module4/src/main/java/com/hithomelabs/princeton1/module4/LinkedQueue.java

@@ -4,71 +4,28 @@ import javax.annotation.Nonnull;
 import java.util.Iterator;
 
 public class LinkedQueue<E> extends Queue<E>{
-
-    Node head;
-    Node tail;
-    int size;
-
-    private class Node{
-        E value;
-        Node next;
-
-        Node(E value){
-            this.value = value;
-        }
-    }
-
     @Override
     public boolean isEmpty() {
-        return size==0;
+        return false;
     }
 
     @Override
     public E dequeue() {
-        if(isEmpty())
-            return null;
-        E element = head.value;
-        // Only a single element is present
-        if (head == tail){
-            tail = null;
-        }
-        head = head.next;
-        --size;
-        return element;
+        return null;
     }
 
     @Override
     public void enqueue(E element) {
-        Node newNode = new Node(element);
-        if(isEmpty())
-            head = newNode;
-        else
-            tail.next = newNode;
-        tail = newNode;
-        ++size;
+
     }
 
     @Override
     public int size() {
-        return size;
+        return 0;
     }
 
     @Override
-    @Nonnull
     public Iterator<E> iterator() {
-        return new Iterator<E>() {
-            Node current = head;
-            @Override
-            public boolean hasNext() {
-                return current != null;
-            }
-
-            @Override
-            public E next() {
-                E element = current.value;
-                current = current.next;
-                return element;
-            }
-        };
+        return null;
     }
 }

module4/src/main/java/com/hithomelabs/princeton1/module4/LinkedStack.java

@@ -3,70 +3,28 @@ import java.util.Iterator;
 
 // Creating a concrete linked Implementation of Stack
 public class LinkedStack<E> extends Stack<E>{
-
-    // No need for an explicit constructor as size will be initialized to 0 and root to null
-    private int size;
-    private Node first;
-
-    // By default instance variables are package private
-    private class Node{
-        E value;
-        Node next;
-    }
-
-    // Will return true if size is 0
     @Override
     public boolean isEmpty() {
-        return (this.size == 0);
+        return false;
     }
 
-    // Adds an element to the start of a linked list
     @Override
     public void push(E element) {
-        Node newNode = new Node();
-        newNode.value = element;
-        newNode.next = first;
-        first = newNode;
-        this.size = this.size + 1;
+
     }
 
     @Override
     public E pop() {
-        if (this.isEmpty())
-            return null;
-        else{
-            Node toBePopped = first;
-            first = first.next;
-            this.size = this.size - 1;
-            return toBePopped.value;
-        }
+        return null;
     }
 
     @Override
     public int size() {
-        return this.size;
+        return 0;
     }
 
     @Override
     public Iterator<E> iterator() {
-        return new Iterator<E>() {
-
-            // Internal classes can access outer objects
-            Node current = first;
-            @Override
-            public boolean hasNext() {
-                return current != null;
-            }
-
-            @Override
-            public E next() {
-                E element = current.value;
-                current = current.next;
-                return element;
-            }
-        };
+        return null;
     }
-
-
-
 }

module5/src/main/java/com/hithomelabs/princeton1/module5/AbstractCustomSorts.java

@@ -4,12 +4,11 @@ public abstract class AbstractCustomSorts<E> {
 
     public abstract void sort(E[] arr);
 
+    // TODO: Implement this method
     public void exch(E[] arr, int j, int i) {
-        E temp = arr[i];
-        arr[i] = arr[j];
-        arr[j] = temp;
     }
 
+    // TODO: Implement this method
     public boolean less(Comparable<E> e1, E e2) {
         return e1.compareTo(e2) < 0;
     }

module5/src/main/java/com/hithomelabs/princeton1/module5/Insertion.java

@@ -1,23 +1,9 @@
 package com.hithomelabs.princeton1.module5;
 
 public class Insertion<E> extends AbstractCustomSorts<E> {
-
-    public void sort(E[] arr){
-        if (arr == null) return;
-        else{
-            int N = arr.length;
-            // * * swap arr[i] with each element greater to it's left
-            for (int i = 1; i < N; i++){
-                int j = i;
-                while(j >= 1 && less((Comparable<E>)arr[j], arr[j-1])){
-                    exch(arr, j, j-1);
-                    j = j-1;
-                }
-            }
-        }
-
-    }
-
+    @Override
+    public void sort(E[] arr) {
 
     }
+}
 

module5/src/main/java/com/hithomelabs/princeton1/module5/Selection.java

@@ -1,23 +1,13 @@
 package com.hithomelabs.princeton1.module5;
 
-
+/*
+ * * Selection sort "selects" the smallest element and swaps it with arr[0] of the array
+ * * Then proceeds to do the same swapping arr[i] with arr[i:arr.length-1]
+ */
 public class Selection<E> extends AbstractCustomSorts<E>{
+    @Override
+    public void sort(E[] arr) {
 
-    /*
-    * * Selection sort "selects" the smallest element and swaps it with arr[0] of the array
-    * * Then proceeds to do the same swapping arr[i] with arr[i:arr.length-1]
-    */
-    public void sort(E[] arr){
-        if (arr ==  null) return;
-        Comparable<E>[] arr1 = (Comparable<E>[]) arr;
-        for(int i = 0; i < arr1.length - 1; i++){
-            int minIndex = i;
-            for(int j = i+1; j < arr.length; j ++){
-                if (less((Comparable<E>) arr[j], arr[minIndex])) minIndex = j;
-            }
-            exch(arr, i, minIndex);
-        }
     }
-
 }
 

module5/src/main/java/com/hithomelabs/princeton1/module5/Shell.java

@@ -24,33 +24,10 @@ public class Shell<E> extends AbstractCustomSorts<E> {
  */
     @Override
     public void sort(E[] arr) {
-        MetaData metaData = new MetaData();
-        int N = arr.length;
-        int h = 1;
-        // * * Calculates the largest value of h greater than n
-        while (3 * h + 1 < N) {
-            h = 3 * h + 1;
-        }
-        while (h >= 1) {
-            h = hsort(arr, h, metaData);
-            h = h / 3;
-        }
-        System.out.println("Array sorted (shell sort) with " + metaData.compares + " compares and " + metaData.swaps + " swaps");
     }
 
     private int hsort(E[] arr, int h, MetaData metadata) {
-        int N  = arr.length;
-        for(int i = h; i < N; i++){
-            int j = i;
-            ++metadata.compares;
-            while(j >= h && less((Comparable<E>) arr[j], arr[j-h])){
-                ++metadata.swaps;
-                exch(arr, j, j-h);
-                j = j - h;
-                ++metadata.compares;
-            }
-        }
-        return h;
+        return 0;
     }
     /*
      * Sample implementation of insertion sort as h-sort of h = 1

module6/src/main/java/com/hithomelabs/princeton1/module6/Merge.java

@@ -7,39 +7,6 @@ import java.util.Arrays;
 public class Merge<E> extends AbstractCustomSorts<E> {
     @Override
     public void sort(E[] arr) {
-
-        int N = arr.length;
-        // * * aux is a helper array required for merge
-        E[] aux = Arrays.copyOf(arr, N);
-        mergesort(arr, aux, 0, N-1);
-
-    }
-
-    private void mergesort(E[] arr, E[] aux, int lo, int hi) {
-
-        if (hi <= lo) return;
-        int mid = lo + (hi - lo)/2;
-        mergesort(arr, aux, lo, mid);
-        mergesort(arr, aux, mid+1, hi);
-        merge(arr, aux, lo, mid, hi);
-
-    }
-
-    private void merge(E[] arr, E[] aux, int lo, int mid, int hi) {
-
-        // * * creating backup of original array
-        for (int i = lo; i <= hi; i++)
-            aux[i] = arr[i];
-
-        int i = lo;
-        int j = mid+1;
-        for (int k = lo; k <= hi; k++){
-            // * If i has already reached mid, no need to compare we insert at pointer k
-            if(i > mid) arr[k] = aux[j++];
-            else if(j > hi) arr[k] = aux[i++];
-            else if(less((Comparable<E>) aux[i], aux[j])) arr[k] = aux[i++];
-            else arr[k] = aux[j++];
-        }
     }
 }
 

module7/src/main/java/com/hithomelabs/princeton1/module7/Quick.java

@@ -6,49 +6,6 @@ import com.hithomelabs.princeton1.module5.AbstractCustomSorts;
 public class Quick<E> extends AbstractCustomSorts<E> {
     @Override
     public void sort(E[] arr) {
-        int N = arr.length;
-        quickSort(arr, 0, N - 1);
-    }
-
-    public void altSort(E[] arr) {
-        int N = arr.length;
-        altQuickSort(arr, 0, N-1);
-    }
-
-    private void altQuickSort(E[] arr, int lo, int hi) {
-        if (lo >= hi) return;
-        int i = lo + 1;
-        int j = i;
-        while(j <= hi){
-            if(less((Comparable<E>) arr[j], arr[lo])){
-                exch(arr, i, j);
-                i++;
-            }
-            j++;
-        }
-        exch(arr, i-1, lo);
-        altQuickSort(arr, lo, i-2);
-        altQuickSort(arr, i, hi);
-    }
-
-    private void quickSort(E[] arr, int lo, int hi) {
-
-        if (lo >= hi) return;
-        int i = lo;
-        int j = hi+1;
-        while(true){
-            while(less((Comparable<E>) arr[++i], arr[lo])){
-                if(i == hi) break;
-            }
-            while(!less((Comparable<E>) arr[--j], arr[lo])){
-                if (j == lo ) break;
-            }
-            if(j<=i) break;
-            exch(arr, i , j);
-        }
-        exch(arr, j, lo);
-        quickSort(arr, lo, j-1);
-        quickSort(arr, j+1, hi);
 
     }
 }

module7/src/test/java/com/hithomelabs/princeton1/module7/QuickTest.java

@@ -33,6 +33,8 @@ class QuickTest {
         Assertions.assertArrayEquals(sorted, arr);
     }
 
+    // * * Optional test for alternate sort implmentation
+    /*
     @Test
     @DisplayName("testing Quick sort default implementation")
     public void testAltSort(){
@@ -45,6 +47,8 @@ class QuickTest {
         Apple[] sorted =  apples.toArray(new Apple[apples.size()]);
         Assertions.assertArrayEquals(sorted, arr);
     }
+    */
+
 
 
     @AfterEach

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

@@ -5,35 +5,17 @@ package com.hithomelabs.princeton1.module8;
  * * 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
+    * * Implement sink API to sink a node if it's sub-heap is not heap-order
     */
     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;
-        }
+    public static <T> void swim(T[] arr, int node, int N){
     }
 
     private static <T> void exch(T[] arr, int i, int j){
@@ -43,7 +25,6 @@ public class Heap{
     }
 
     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

@@ -10,22 +10,18 @@ public class HeapSort<E> extends AbstractCustomSorts<E> {
         int N = arr.length;
 
         E[] heapArr = (E[]) new Object[N+1];
-        // * * to simplify we copy original array from
+        // * * to simplify we copy original array and write it to the new array starting index 1
         System.arraycopy(arr, 0, heapArr, 1, N);
-
         // * * An array of size N holds a heap of size N-1
         coreSortingLogic(heapArr, N);
+        // * * Re-copying the sorted array to the original
         System.arraycopy(heapArr, 1, arr, 0, N);
     }
 
+    /*
+     * * Implement the core sorting logic
+     * * P.S the provision of making the index 0 null for ease of use has already been done above
+    */
     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);
-        }
     }
 }