lgrthms/lib/algorithms/sort/heapSort.js

Algorithms and data structures for your JavaScript and TypeScript projects 🧑‍💻

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.heapSort = void 0;
const Comparator_1 = require("../../utils/Comparator");
const arrays_1 = require("../../utils/arrays");
// O(nlog(n)) time | O(1) space
function heapSort(array, compareFn) {
    const comparator = new Comparator_1.Comparator(compareFn);
    buildMaxHeap(array, comparator);
    for (let lastIndex = array.length - 1; lastIndex > 0; lastIndex--) {
        (0, arrays_1.swap)(array, 0, lastIndex);
        siftDown(array, 0, lastIndex - 1, comparator);
    }
    return array;
}
exports.heapSort = heapSort;
function buildMaxHeap(array, comparator) {
    const lastIndex = array.length - 1;
    const firstParentIndex = getParentIndex(lastIndex);
    for (let parentIndex = firstParentIndex; parentIndex >= 0; parentIndex--) {
        siftDown(array, parentIndex, lastIndex, comparator);
    }
}
function siftDown(array, index, lastIndex, comparator) {
    let childOneIndex = getChildIndex(index, lastIndex, 1);
    while (childOneIndex !== -1) {
        const childTwoIndex = getChildIndex(index, lastIndex, 2);
        let childIndexToSwapWith = childOneIndex;
        if (childTwoIndex !== -1 && comparator.isGreaterThan(array[childTwoIndex], array[childOneIndex])) {
            childIndexToSwapWith = childTwoIndex;
        }
        if (comparator.isGreaterThan(array[childIndexToSwapWith], array[index])) {
            (0, arrays_1.swap)(array, index, childIndexToSwapWith);
            index = childIndexToSwapWith;
            childOneIndex = getChildIndex(index, lastIndex, 1);
        }
        else {
            break;
        }
    }
}
function getParentIndex(childIndex) {
    return Math.floor((childIndex - 1) / 2);
}
function getChildIndex(parentIndex, lastIndex, childNumber) {
    const childIndex = parentIndex * 2 + childNumber;
    return childIndex > lastIndex ? -1 : childIndex;
}