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HeapSort.java
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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);
}
}