lgrthms/lib/algorithms/sort/mergeSort.js

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

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.mergeSort = void 0;
const Comparator_1 = require("../../utils/Comparator");
// O(nlog(n)) time | O(n) space
function mergeSort(array, compareFn) {
    const comparator = new Comparator_1.Comparator(compareFn);
    const auxiliaryArray = [...array];
    doMergeSort(array, auxiliaryArray, comparator, 0, array.length - 1);
    return array;
}
exports.mergeSort = mergeSort;
function doMergeSort(mainArray, auxiliaryArray, comparator, startIdx, endIdx) {
    if (startIdx === endIdx) {
        return;
    }
    const middleIdx = Math.floor((startIdx + endIdx) / 2);
    doMergeSort(auxiliaryArray, mainArray, comparator, startIdx, middleIdx);
    doMergeSort(auxiliaryArray, mainArray, comparator, middleIdx + 1, endIdx);
    merge(mainArray, auxiliaryArray, comparator, startIdx, middleIdx, endIdx);
}
function merge(mainArray, auxiliaryArray, comparator, startIdx, middleIdx, endIdx) {
    let sortedIdx = startIdx;
    let leftIdx = startIdx;
    let rightIdx = middleIdx + 1;
    while (leftIdx <= middleIdx && rightIdx <= endIdx) {
        if (comparator.isLessThan(auxiliaryArray[leftIdx], auxiliaryArray[rightIdx])) {
            mainArray[sortedIdx] = auxiliaryArray[leftIdx];
            leftIdx++;
        }
        else {
            mainArray[sortedIdx] = auxiliaryArray[rightIdx];
            rightIdx++;
        }
        sortedIdx++;
    }
    while (leftIdx <= middleIdx) {
        mainArray[sortedIdx] = auxiliaryArray[leftIdx];
        leftIdx++;
        sortedIdx++;
    }
    while (rightIdx <= endIdx) {
        mainArray[sortedIdx] = auxiliaryArray[rightIdx];
        rightIdx++;
        sortedIdx++;
    }
}