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clean up Heap implementation (#184)

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Kevin Brewer 2018-08-30 00:11:14 -05:00 committed by Oleksii Trekhleb
parent a8d7435b8d
commit bc50fff2ee
1 changed files with 18 additions and 21 deletions
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39
src/data-structures/heap/Heap.js
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@ -47,7 +47,7 @@ export default class Heap {
* @return {boolean}
*/
hasParent(childIndex) {
return this.getParentIndex(childIndex) >= 0;
return childIndex > 0;
}
/**
@ -144,17 +144,16 @@ export default class Heap {
/**
* @param {*} item
* @param {Comparator} [customFindingComparator]
* @param {Comparator} [customComparator]
* @return {Heap}
*/
remove(item, customFindingComparator) {
remove(item, customComparator = this.compare) {
// Find number of items to remove.
const customComparator = customFindingComparator || this.compare;
const numberOfItemsToRemove = this.find(item, customComparator).length;
for (let iteration = 0; iteration < numberOfItemsToRemove; iteration += 1) {
// We need to find item index to remove each time after removal since
// indices are being change after each heapify process.
// indices are being changed after each heapify process.
const indexToRemove = this.find(item, customComparator).pop();
// If we need to remove last child in the heap then just remove it.
@ -165,16 +164,14 @@ export default class Heap {
// Move last element in heap to the vacant (removed) position.
this.heapContainer[indexToRemove] = this.heapContainer.pop();
// Get parent.
const parentItem = this.hasParent(indexToRemove) ? this.parent(indexToRemove) : null;
const leftChild = this.hasLeftChild(indexToRemove) ? this.leftChild(indexToRemove) : null;
const parentItem = this.parent(indexToRemove);
// If there is no parent or parent is in incorrect order with the node
// If there is no parent or parent is in correct order with the node
// we're going to delete then heapify down. Otherwise heapify up.
if (
leftChild !== null
this.hasLeftChild(indexToRemove)
&& (
parentItem === null
parentItem == null
|| this.pairIsInCorrectOrder(parentItem, this.heapContainer[indexToRemove])
)
) {
@ -193,12 +190,11 @@ export default class Heap {
* @param {Comparator} [customComparator]
* @return {Number[]}
*/
find(item, customComparator) {
find(item, customComparator = this.compare) {
const foundItemIndices = [];
const comparator = customComparator || this.compare;
for (let itemIndex = 0; itemIndex < this.heapContainer.length; itemIndex += 1) {
if (comparator.equal(item, this.heapContainer[itemIndex])) {
if (customComparator.equal(item, this.heapContainer[itemIndex])) {
foundItemIndices.push(itemIndex);
}
}
@ -224,9 +220,9 @@ export default class Heap {
* @param {number} [customStartIndex]
*/
heapifyUp(customStartIndex) {
// Take last element (last in array or the bottom left in a tree) in
// a heap container and lift him up until we find the parent element
// that is less then the current new one.
// Take the last element (last in array or the bottom left in a tree)
// in the heap container and lift it up until it is in the correct
// order with respect to its parent element.
let currentIndex = customStartIndex || this.heapContainer.length - 1;
while (
@ -241,10 +237,11 @@ export default class Heap {
/**
* @param {number} [customStartIndex]
*/
heapifyDown(customStartIndex) {
// Compare the root element to its children and swap root with the smallest
// of children. Do the same for next children after swap.
let currentIndex = customStartIndex || 0;
heapifyDown(customStartIndex = 0) {
// Compare the parent element to its children and swap parent with the appropriate
// child (smallest child for MinHeap, largest child for MaxHeap).
// Do the same for next children after swap.
let currentIndex = customStartIndex;
let nextIndex = null;
while (this.hasLeftChild(currentIndex)) {