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- //
- // ******************PUBLIC OPERATIONS*********************
- // void insert( x ) --> Insert x
- // Comparable deleteMin( )--> Return and remove smallest item
- // Comparable findMin( ) --> Return smallest item
- // boolean isEmpty( ) --> Return true if empty; else false
- // ******************ERRORS********************************
- // Throws RuntimeException for findMin and deleteMin when empty
-
- package org.insa.algo.utils;
-
- import java.util.ArrayList;
-
- /**
- * Implements a binary heap. Note that all "matching" is based on the compareTo
- * method.
- *
- * @author Mark Allen Weiss
- * @author DLB
- */
- public class BinaryHeap<E extends Comparable<E>> implements PriorityQueue<E> {
-
- // Number of elements in heap.
- private int currentSize;
-
- // The heap array.
- private final ArrayList<E> array;
-
- /**
- * Construct a new empty binary heap.
- */
- public BinaryHeap() {
- this.currentSize = 0;
- this.array = new ArrayList<E>();
- }
-
- /**
- * Construct a copy of the given heap.
- *
- * @param heap Binary heap to copy.
- */
- public BinaryHeap(BinaryHeap<E> heap) {
- this.currentSize = heap.currentSize;
- this.array = new ArrayList<E>(heap.array);
- }
-
- /**
- * Set an element at the given index.
- *
- * @param index Index at which the element should be set.
- * @param value Element to set.
- */
- private void arraySet(int index, E value) {
- if (index == this.array.size()) {
- this.array.add(value);
- }
- else {
- this.array.set(index, value);
- }
- }
-
- /**
- * @return Index of the parent of the given index.
- */
- private int index_parent(int index) {
- return (index - 1) / 2;
- }
-
- /**
- * @return Index of the left child of the given index.
- */
- private int index_left(int index) {
- return index * 2 + 1;
- }
-
- /**
- * Internal method to percolate up in the heap.
- *
- * @param index Index at which the percolate begins.
- */
- private void percolateUp(int index) {
- E x = this.array.get(index);
-
- for (; index > 0
- && x.compareTo(this.array.get(index_parent(index))) < 0; index = index_parent(
- index)) {
- E moving_val = this.array.get(index_parent(index));
- this.arraySet(index, moving_val);
- }
-
- this.arraySet(index, x);
- }
-
- /**
- * Internal method to percolate down in the heap.
- *
- * @param index Index at which the percolate begins.
- */
- private void percolateDown(int index) {
- int ileft = index_left(index);
- int iright = ileft + 1;
-
- if (ileft < this.currentSize) {
- E current = this.array.get(index);
- E left = this.array.get(ileft);
- boolean hasRight = iright < this.currentSize;
- E right = (hasRight) ? this.array.get(iright) : null;
-
- if (!hasRight || left.compareTo(right) < 0) {
- // Left is smaller
- if (left.compareTo(current) < 0) {
- this.arraySet(index, left);
- this.arraySet(ileft, current);
- this.percolateDown(ileft);
- }
- }
- else {
- // Right is smaller
- if (right.compareTo(current) < 0) {
- this.arraySet(index, right);
- this.arraySet(iright, current);
- this.percolateDown(iright);
- }
- }
- }
- }
-
- @Override
- public boolean isEmpty() {
- return this.currentSize == 0;
- }
-
- @Override
- public int size() {
- return this.currentSize;
- }
-
- @Override
- public void insert(E x) {
- int index = this.currentSize++;
- this.arraySet(index, x);
- this.percolateUp(index);
- }
-
- @Override
- public void remove(E x) throws ElementNotFoundException {
- // TODO:
- }
-
- @Override
- public E findMin() throws EmptyPriorityQueueException {
- if (isEmpty())
- throw new RuntimeException("Empty binary heap.");
- return this.array.get(0);
- }
-
- @Override
- public E deleteMin() throws EmptyPriorityQueueException {
- E minItem = findMin();
- E lastItem = this.array.get(--this.currentSize);
- this.arraySet(0, lastItem);
- this.percolateDown(0);
- return minItem;
- }
-
- /**
- * Prints the heap
- */
- public void print() {
- System.out.println();
- System.out.println("======== HEAP (size = " + this.currentSize + ") ========");
- System.out.println();
-
- for (int i = 0; i < this.currentSize; i++) {
- System.out.println(this.array.get(i).toString());
- }
-
- System.out.println();
- System.out.println("-------- End of heap --------");
- System.out.println();
- }
-
- /**
- * Prints the elements of the heap according to their respective order.
- */
- public void printSorted() {
-
- BinaryHeap<E> copy = new BinaryHeap<E>(this);
-
- System.out.println();
- System.out.println("======== Sorted HEAP (size = " + this.currentSize + ") ========");
- System.out.println();
-
- while (!copy.isEmpty()) {
- System.out.println(copy.deleteMin());
- }
-
- System.out.println();
- System.out.println("-------- End of heap --------");
- System.out.println();
- }
-
- }
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