130 lines
3.6 KiB
Java
130 lines
3.6 KiB
Java
package Sorts;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.List;
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import static Sorts.SortUtils.*;
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/**
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* Heap Sort Algorithm
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* Implements MinHeap
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*
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* @author Podshivalov Nikita (https://github.com/nikitap492)
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*/
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public class HeapSort implements SortAlgorithm {
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private static class Heap<T extends Comparable<T>> {
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/**
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* Array to store heap
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*/
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private T[] heap;
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/**
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* Constructor
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*
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* @param heap array of unordered integers
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*/
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public Heap(T[] heap) {
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this.heap = heap;
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}
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/**
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* Heapifies subtree from top as root to last as last child
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*
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* @param rootIndex index of root
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* @param lastChild index of last child
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*/
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private void heapSubtree(int rootIndex, int lastChild) {
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int leftIndex = rootIndex * 2 + 1;
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int rightIndex = rootIndex * 2 + 2;
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T root = heap[rootIndex];
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if (rightIndex <= lastChild) { // if has right and left children
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T left = heap[leftIndex];
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T right = heap[rightIndex];
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if (less(left, right) && less(left, root)) {
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swap(heap, leftIndex, rootIndex);
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heapSubtree(leftIndex, lastChild);
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} else if (less(right, root)) {
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swap(heap, rightIndex, rootIndex);
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heapSubtree(rightIndex, lastChild);
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}
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} else if (leftIndex <= lastChild) { // if no right child, but has left child
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T left = heap[leftIndex];
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if (less(left, root)) {
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swap(heap, leftIndex, rootIndex);
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heapSubtree(leftIndex, lastChild);
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}
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}
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}
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/**
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* Makes heap with root as root
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*
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* @param root index of root of heap
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*/
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private void makeMinHeap(int root) {
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int leftIndex = root * 2 + 1;
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int rightIndex = root * 2 + 2;
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boolean hasLeftChild = leftIndex < heap.length;
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boolean hasRightChild = rightIndex < heap.length;
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if (hasRightChild) { //if has left and right
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makeMinHeap(leftIndex);
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makeMinHeap(rightIndex);
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heapSubtree(root, heap.length - 1);
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} else if (hasLeftChild) {
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heapSubtree(root, heap.length - 1);
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}
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}
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/**
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* Gets the root of heap
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*
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* @return root of heap
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*/
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private T getRoot(int size) {
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swap(heap, 0, size);
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heapSubtree(0, size - 1);
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return heap[size]; // return old root
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}
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}
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@Override
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public <T extends Comparable<T>> T[] sort(T[] unsorted) {
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return sort(Arrays.asList(unsorted)).toArray(unsorted);
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}
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@Override
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public <T extends Comparable<T>> List<T> sort(List<T> unsorted) {
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int size = unsorted.size();
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@SuppressWarnings("unchecked")
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Heap<T> heap = new Heap<>(unsorted.toArray((T[]) new Comparable[unsorted.size()]));
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heap.makeMinHeap(0); // make min heap using index 0 as root.
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List<T> sorted = new ArrayList<>(size);
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while (size > 0) {
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T min = heap.getRoot(--size);
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sorted.add(min);
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}
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return sorted;
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}
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/**
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* Main method
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*
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* @param args the command line arguments
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*/
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public static void main(String[] args) {
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Integer[] heap = {4, 23, 6, 78, 1, 54, 231, 9, 12};
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HeapSort heapSort = new HeapSort();
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print(heapSort.sort(heap));
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}
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}
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