Merge pull request #1 from ShyamW/master

Implemented HeapSort

Author: dynamitechetan

HeapSort.java

@@ -0,0 +1,185 @@
+import java.util.Scanner;
+
+/**
+ * Heap Sort Algorithm. Implements MinHeap
+ *
+ */
+public class HeapSort {
+    /**
+     * array to store heap.
+     */
+    private int[] heap;
+    /**
+     * size of heap.
+     */
+    private int size;
+
+    /**
+     * Constructor.
+     *
+     * @param heap
+     *            array of unordered integers
+     */
+    public HeapSort(int[] heap) {
+        this.setHeap(heap);
+        this.setSize(heap.length);
+    }
+
+    /**
+     * Sets this.size with {@code length).
+     *
+     * @param length
+     *            integer length of heap
+     */
+    private void setSize(int length) {
+        this.size = length;
+    }
+
+    /**
+     * Sets Heap with {@code heap}.
+     *
+     * @param heap
+     *            array of unordered elements
+     */
+    private void setHeap(int[] heap) {
+        this.heap = heap;
+    }
+
+    /**
+     * Swaps index of {@code first} with {@code second}.
+     *
+     * @param first
+     *            index to swap {@code second} with
+     * @param second
+     *            index to swap {@code first} with
+     */
+    private void swap(int first, int second) {
+        int temp = this.heap[first];
+        this.heap[first] = this.heap[second];
+        this.heap[second] = temp;
+    }
+
+    /**
+     * Heapifies subtree from {@code top} as root to {@code last} as last child.
+     *
+     * @param rootIndex
+     *            index of root
+     * @param lastChild
+     *            index of last child
+     */
+    private void heapSubtree(int rootIndex, int lastChild) {
+        int leftIndex = rootIndex * 2 + 1; 
+        int rightIndex = rootIndex * 2 + 2;
+        int root = this.heap[rootIndex];
+        if (rightIndex <= lastChild) { // if has right and left children
+            int left = this.heap[leftIndex]; 
+            int right = this.heap[rightIndex]; 
+            if (left < right && left < root) {
+                this.swap(leftIndex, rootIndex); 
+                this.heapSubtree(leftIndex, lastChild);
+            } else if (right < root) {
+                this.swap(rightIndex, rootIndex);
+                this.heapSubtree(rightIndex, lastChild);
+            }
+        } else if (leftIndex <= lastChild) { // if no right child, but has left child
+            int left = this.heap[leftIndex];
+            if (left < root) {
+                this.swap(leftIndex, rootIndex);
+                this.heapSubtree(leftIndex, lastChild);
+            }
+        }
+    }
+
+    /**
+     * Makes heap with {@code root} as root.
+     *
+     * @param root
+     *            index of root of heap
+     */
+    private void makeMinHeap(int root) {
+        int leftIndex = root * 2 + 1; 
+        int rightIndex = root * 2 + 2; 
+        boolean hasLeftChild = leftIndex < this.heap.length;
+        boolean hasRightChild = rightIndex < this.heap.length;
+        if (hasRightChild) { //if has left and right
+            this.makeMinHeap(leftIndex);
+            this.makeMinHeap(rightIndex);
+            this.heapSubtree(root, this.heap.length - 1);
+        } else if (hasLeftChild) {
+            this.heapSubtree(root, this.heap.length - 1);
+        }
+    }
+
+    /**
+     * Gets the root of this.heap.
+     *
+     * @return root of this.heap
+     */
+    private int getRoot() {
+        this.swap(0, this.size - 1);
+        this.size--;
+        this.heapSubtree(0, this.size - 1);
+        return this.heap[this.size]; // return old root
+    }
+
+    /**
+     * Sorts this.heap with heap sort; displays ordered elements to console.
+     *
+     * @return {@code sorted} array of sorted elements
+     */
+    public final int[] sort() {
+        this.makeMinHeap(0); // make min heap using index 0 as root.
+        int[] sorted = new int[this.size];
+        int index = 0;
+        while (this.size > 0) {
+            int min = this.getRoot();
+            sorted[index] = min;
+            index++;
+        }
+        return sorted;
+    }
+
+    /**
+     * Gets input to sort.
+     *
+     * @return unsorted array of integers to sort
+     */
+    public static int[] getInput() {
+        final int numElements = 6;
+        int[] unsorted = new int[numElements];
+        Scanner input = new Scanner(System.in);
+        System.out.println("Enter any 6 Numbers for Unsorted Array : ");
+        for (int i = 0; i < numElements; i++) {
+            unsorted[i] = input.nextInt();
+        }
+        input.close();
+        return unsorted;
+    }
+
+    /**
+     * Prints elements in heap.
+     *
+     * @param heap
+     *            array representing heap
+     */
+    public static void printData(int[] heap) {
+        System.out.println("Sorted Elements:");
+        for (int i = 0; i < heap.length; i++) {
+            System.out.print(" " + heap[i] + " ");
+        }
+    }
+
+    /**
+     * Main method.
+     *
+     * @param args
+     *            the command line arguments
+     */
+    public static void main(String[] args) {
+        int[] heap = getInput();
+        HeapSort data = new HeapSort(heap);
+        int[] sorted = data.sort();
+        printData(sorted);
+    }
+
+}