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| 1 | +import java.util.Scanner; |
| 2 | + |
| 3 | +/** |
| 4 | + * Heap Sort Algorithm. |
| 5 | + * |
| 6 | + */ |
| 7 | +public class HeapSort { |
| 8 | + /** |
| 9 | + * array to store heap. |
| 10 | + */ |
| 11 | + private int[] heap; |
| 12 | + /** |
| 13 | + * size of heap. |
| 14 | + */ |
| 15 | + private int size; |
| 16 | + |
| 17 | + /** |
| 18 | + * Constructor. |
| 19 | + * |
| 20 | + * @param heap |
| 21 | + * array of unordered integers |
| 22 | + */ |
| 23 | + public HeapSort(int[] heap) { |
| 24 | + this.setHeap(heap); |
| 25 | + this.setSize(heap.length); |
| 26 | + } |
| 27 | + |
| 28 | + /** |
| 29 | + * Sets this.size with {@code length). |
| 30 | + * |
| 31 | + * @param length |
| 32 | + * integer length of heap |
| 33 | + */ |
| 34 | + private void setSize(int length) { |
| 35 | + this.size = length; |
| 36 | + } |
| 37 | + |
| 38 | + /** |
| 39 | + * Sets Heap with {@code heap}. |
| 40 | + * |
| 41 | + * @param heap |
| 42 | + * array of unordered elements |
| 43 | + */ |
| 44 | + private void setHeap(int[] heap) { |
| 45 | + this.heap = heap; |
| 46 | + } |
| 47 | + |
| 48 | + /** |
| 49 | + * Swaps index of {@code first} with {@code second}. |
| 50 | + * |
| 51 | + * @param first |
| 52 | + * index to swap {@code second} with |
| 53 | + * @param second |
| 54 | + * index to swap {@code first} with |
| 55 | + */ |
| 56 | + private void swap(int first, int second) { |
| 57 | + int temp = this.heap[first]; |
| 58 | + this.heap[first] = this.heap[second]; |
| 59 | + this.heap[second] = temp; |
| 60 | + } |
| 61 | + |
| 62 | + /** |
| 63 | + * Heapifies subtree from {@code top} as root to {@code last} as last child. |
| 64 | + * |
| 65 | + * @param rootIndex |
| 66 | + * index of root |
| 67 | + * @param lastChild |
| 68 | + * index of last child |
| 69 | + */ |
| 70 | + private void heapSubtree(int rootIndex, int lastChild) { |
| 71 | + int leftIndex = rootIndex * 2 + 1; // calculate index of left children |
| 72 | + int rightIndex = rootIndex * 2 + 2; |
| 73 | + boolean hasLeftChild = leftIndex <= lastChild; |
| 74 | + boolean hasRightChild = rightIndex <= lastChild; |
| 75 | + int root = this.heap[rootIndex]; |
| 76 | + if (hasRightChild) { |
| 77 | + int left = this.heap[leftIndex]; // get left child |
| 78 | + int right = this.heap[rightIndex]; // get right child |
| 79 | + if (left < right && left < root) { |
| 80 | + this.swap(leftIndex, rootIndex); //swap left with root |
| 81 | + this.heapSubtree(leftIndex, lastChild); |
| 82 | + } else if (right < root) { |
| 83 | + this.swap(rightIndex, rootIndex); //swap right with root |
| 84 | + this.heapSubtree(rightIndex, lastChild); |
| 85 | + } |
| 86 | + } else if (hasLeftChild) { // if no right, but has left |
| 87 | + int left = this.heap[leftIndex]; |
| 88 | + if (left < root) { |
| 89 | + this.swap(leftIndex, rootIndex); //swap left and root |
| 90 | + this.heapSubtree(leftIndex, lastChild); |
| 91 | + } |
| 92 | + } |
| 93 | + } |
| 94 | + |
| 95 | + /** |
| 96 | + * Makes heap with {@code root} as root. |
| 97 | + * |
| 98 | + * @param root |
| 99 | + * index of root of heap |
| 100 | + */ |
| 101 | + private void makeMinHeap(int root) { |
| 102 | + int leftIndex = root * 2 + 1; // calculate index of left child |
| 103 | + int rightIndex = root * 2 + 2; // calculate index of left child |
| 104 | + boolean hasLeftChild = leftIndex < this.heap.length; |
| 105 | + boolean hasRightChild = rightIndex < this.heap.length; |
| 106 | + if (hasRightChild) { //if has left and right |
| 107 | + this.makeMinHeap(leftIndex); |
| 108 | + this.makeMinHeap(rightIndex); |
| 109 | + this.heapSubtree(root, this.heap.length - 1); |
| 110 | + } else if (hasLeftChild) { |
| 111 | + this.heapSubtree(root, this.heap.length - 1); |
| 112 | + } |
| 113 | + } |
| 114 | + |
| 115 | + /** |
| 116 | + * Gets the root of this.heap. |
| 117 | + * |
| 118 | + * @return root of this.heap |
| 119 | + */ |
| 120 | + private int getRoot() { |
| 121 | + this.swap(0, this.size - 1); |
| 122 | + this.size--; |
| 123 | + this.heapSubtree(0, this.size - 1); |
| 124 | + return this.heap[this.size]; // return old root |
| 125 | + } |
| 126 | + |
| 127 | + /** |
| 128 | + * Sorts this.heap with heap sort; displays ordered elements to console. |
| 129 | + * |
| 130 | + * @return {@code sorted} array of sorted elements |
| 131 | + */ |
| 132 | + public final int[] sort() { |
| 133 | + this.makeMinHeap(0); // make min heap using index 0 as root. |
| 134 | + int[] sorted = new int[this.size]; |
| 135 | + int index = 0; |
| 136 | + while (this.size > 0) { |
| 137 | + int min = this.getRoot(); |
| 138 | + sorted[index] = min; |
| 139 | + index++; |
| 140 | + } |
| 141 | + return sorted; |
| 142 | + } |
| 143 | + |
| 144 | + /** |
| 145 | + * Gets input to sort. |
| 146 | + * |
| 147 | + * @return unsorted array of integers to sort |
| 148 | + */ |
| 149 | + public static int[] getInput() { |
| 150 | + final int numElements = 6; |
| 151 | + int[] unsorted = new int[numElements]; |
| 152 | + Scanner input = new Scanner(System.in); |
| 153 | + System.out.println("Enter any 6 Numbers for Unsorted Array : "); |
| 154 | + for (int i = 0; i < numElements; i++) { |
| 155 | + unsorted[i] = input.nextInt(); |
| 156 | + } |
| 157 | + input.close(); |
| 158 | + return unsorted; |
| 159 | + } |
| 160 | + |
| 161 | + /** |
| 162 | + * Prints elements in heap. |
| 163 | + * |
| 164 | + * @param heap |
| 165 | + * array representing heap |
| 166 | + */ |
| 167 | + public static void printData(int[] heap) { |
| 168 | + System.out.println("Sorted Elements:"); |
| 169 | + for (int i = 0; i < heap.length; i++) { |
| 170 | + System.out.print(" " + heap[i] + " "); |
| 171 | + } |
| 172 | + } |
| 173 | + |
| 174 | + /** |
| 175 | + * Main method. |
| 176 | + * |
| 177 | + * @param args |
| 178 | + * the command line arguments |
| 179 | + */ |
| 180 | + public static void main(String[] args) { |
| 181 | + int[] heap = getInput(); |
| 182 | + HeapSort data = new HeapSort(heap); |
| 183 | + int[] sorted = data.sort(); |
| 184 | + printData(sorted); |
| 185 | + } |
| 186 | + |
| 187 | +} |
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