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clean up Heap implementation (#184)
This commit is contained in:

committed by
Oleksii Trekhleb

parent
a8d7435b8d
commit
bc50fff2ee
@ -47,7 +47,7 @@ export default class Heap {
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* @return {boolean}
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* @return {boolean}
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*/
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*/
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hasParent(childIndex) {
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hasParent(childIndex) {
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return this.getParentIndex(childIndex) >= 0;
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return childIndex > 0;
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}
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}
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/**
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/**
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@ -144,17 +144,16 @@ export default class Heap {
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/**
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/**
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* @param {*} item
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* @param {*} item
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* @param {Comparator} [customFindingComparator]
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* @param {Comparator} [customComparator]
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* @return {Heap}
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* @return {Heap}
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*/
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*/
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remove(item, customFindingComparator) {
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remove(item, customComparator = this.compare) {
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// Find number of items to remove.
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// Find number of items to remove.
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const customComparator = customFindingComparator || this.compare;
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const numberOfItemsToRemove = this.find(item, customComparator).length;
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const numberOfItemsToRemove = this.find(item, customComparator).length;
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for (let iteration = 0; iteration < numberOfItemsToRemove; iteration += 1) {
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for (let iteration = 0; iteration < numberOfItemsToRemove; iteration += 1) {
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// We need to find item index to remove each time after removal since
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// We need to find item index to remove each time after removal since
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// indices are being change after each heapify process.
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// indices are being changed after each heapify process.
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const indexToRemove = this.find(item, customComparator).pop();
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const indexToRemove = this.find(item, customComparator).pop();
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// If we need to remove last child in the heap then just remove it.
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// If we need to remove last child in the heap then just remove it.
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@ -165,16 +164,14 @@ export default class Heap {
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// Move last element in heap to the vacant (removed) position.
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// Move last element in heap to the vacant (removed) position.
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this.heapContainer[indexToRemove] = this.heapContainer.pop();
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this.heapContainer[indexToRemove] = this.heapContainer.pop();
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// Get parent.
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const parentItem = this.parent(indexToRemove);
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const parentItem = this.hasParent(indexToRemove) ? this.parent(indexToRemove) : null;
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const leftChild = this.hasLeftChild(indexToRemove) ? this.leftChild(indexToRemove) : null;
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// If there is no parent or parent is in incorrect order with the node
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// If there is no parent or parent is in correct order with the node
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// we're going to delete then heapify down. Otherwise heapify up.
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// we're going to delete then heapify down. Otherwise heapify up.
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if (
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if (
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leftChild !== null
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this.hasLeftChild(indexToRemove)
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&& (
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&& (
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parentItem === null
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parentItem == null
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|| this.pairIsInCorrectOrder(parentItem, this.heapContainer[indexToRemove])
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|| this.pairIsInCorrectOrder(parentItem, this.heapContainer[indexToRemove])
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)
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)
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) {
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) {
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@ -193,12 +190,11 @@ export default class Heap {
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* @param {Comparator} [customComparator]
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* @param {Comparator} [customComparator]
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* @return {Number[]}
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* @return {Number[]}
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*/
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*/
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find(item, customComparator) {
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find(item, customComparator = this.compare) {
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const foundItemIndices = [];
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const foundItemIndices = [];
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const comparator = customComparator || this.compare;
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for (let itemIndex = 0; itemIndex < this.heapContainer.length; itemIndex += 1) {
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for (let itemIndex = 0; itemIndex < this.heapContainer.length; itemIndex += 1) {
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if (comparator.equal(item, this.heapContainer[itemIndex])) {
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if (customComparator.equal(item, this.heapContainer[itemIndex])) {
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foundItemIndices.push(itemIndex);
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foundItemIndices.push(itemIndex);
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}
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}
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}
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}
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@ -224,9 +220,9 @@ export default class Heap {
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* @param {number} [customStartIndex]
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* @param {number} [customStartIndex]
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*/
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*/
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heapifyUp(customStartIndex) {
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heapifyUp(customStartIndex) {
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// Take last element (last in array or the bottom left in a tree) in
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// Take the last element (last in array or the bottom left in a tree)
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// a heap container and lift him up until we find the parent element
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// in the heap container and lift it up until it is in the correct
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// that is less then the current new one.
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// order with respect to its parent element.
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let currentIndex = customStartIndex || this.heapContainer.length - 1;
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let currentIndex = customStartIndex || this.heapContainer.length - 1;
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while (
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while (
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@ -241,10 +237,11 @@ export default class Heap {
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/**
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/**
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* @param {number} [customStartIndex]
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* @param {number} [customStartIndex]
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*/
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*/
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heapifyDown(customStartIndex) {
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heapifyDown(customStartIndex = 0) {
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// Compare the root element to its children and swap root with the smallest
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// Compare the parent element to its children and swap parent with the appropriate
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// of children. Do the same for next children after swap.
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// child (smallest child for MinHeap, largest child for MaxHeap).
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let currentIndex = customStartIndex || 0;
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// Do the same for next children after swap.
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let currentIndex = customStartIndex;
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let nextIndex = null;
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let nextIndex = null;
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while (this.hasLeftChild(currentIndex)) {
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while (this.hasLeftChild(currentIndex)) {
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