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Use Comparator in heap.

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Oleksii Trekhleb
2018-04-12 08:25:19 +03:00
parent 953d9e0fb8
commit e05d159765
2 changed files with 9 additions and 18 deletions
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23
src/data-structures/heap/MinHeap.js
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@ -1,7 +1,10 @@
import Comparator from '../../utils/comparator/Comparator';
export default class MinHeap { export default class MinHeap {
constructor() { constructor() {
// Array representation of the heap. // Array representation of the heap.
this.heapContainer = []; this.heapContainer = [];
this.compare = new Comparator();
} }
static getLeftChildIndex(parentIndex) { static getLeftChildIndex(parentIndex) {
@ -85,7 +88,7 @@ export default class MinHeap {
while ( while (
MinHeap.hasParent(currentIndex) && MinHeap.hasParent(currentIndex) &&
this.lessThen(this.heapContainer[currentIndex], this.parent(currentIndex)) this.compare.lessThen(this.heapContainer[currentIndex], this.parent(currentIndex))
) { ) {
this.swap(currentIndex, MinHeap.getParentIndex(currentIndex)); this.swap(currentIndex, MinHeap.getParentIndex(currentIndex));
currentIndex = MinHeap.getParentIndex(currentIndex); currentIndex = MinHeap.getParentIndex(currentIndex);
@ -101,14 +104,14 @@ export default class MinHeap {
while (this.hasLeftChild(currentIndex)) { while (this.hasLeftChild(currentIndex)) {
if ( if (
this.hasRightChild(currentIndex) && this.hasRightChild(currentIndex) &&
this.lessThen(this.rightChild(currentIndex), this.leftChild(currentIndex)) this.compare.lessThen(this.rightChild(currentIndex), this.leftChild(currentIndex))
) { ) {
nextIndex = MinHeap.getRightChildIndex(currentIndex); nextIndex = MinHeap.getRightChildIndex(currentIndex);
} else { } else {
nextIndex = MinHeap.getLeftChildIndex(currentIndex); nextIndex = MinHeap.getLeftChildIndex(currentIndex);
} }
if (this.lessThen(this.heapContainer[currentIndex], this.heapContainer[nextIndex])) { if (this.compare.lessThen(this.heapContainer[currentIndex], this.heapContainer[nextIndex])) {
break; break;
} }
@ -120,18 +123,4 @@ export default class MinHeap {
toString() { toString() {
return this.heapContainer.toString(); return this.heapContainer.toString();
} }
compare(a, b) {
if (a === b) {
return 0;
}
// Min heap may be converted to max heap by simply changing this line to:
// a > b ? -1 : 1
return a < b ? -1 : 1;
}
lessThen(a, b) {
return this.compare(a, b) === -1;
}
} }

4
src/data-structures/priority-queue/PriorityQueue.js
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@ -1,4 +1,5 @@
import MinHeap from '../heap/MinHeap'; import MinHeap from '../heap/MinHeap';
import Comparator from '../../utils/comparator/Comparator';
// It is the same as min heap except that when comparing to elements // It is the same as min heap except that when comparing to elements
// we take into account not element's value but rather its priority. // we take into account not element's value but rather its priority.
@ -6,6 +7,7 @@ export default class PriorityQueue extends MinHeap {
constructor() { constructor() {
super(); super();
this.priorities = {}; this.priorities = {};
this.compare = new Comparator(this.comparePriority.bind(this));
} }
add(item, priority = 0) { add(item, priority = 0) {
@ -13,7 +15,7 @@ export default class PriorityQueue extends MinHeap {
super.add(item); super.add(item);
} }
compare(a, b) { comparePriority(a, b) {
if (this.priorities[a] === this.priorities[b]) { if (this.priorities[a] === this.priorities[b]) {
return 0; return 0;
} }