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Commit ddf6ce7

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add quicksort method, still need to add better heuristic for choosing pivot points
1 parent 74329cd commit ddf6ce7

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4 files changed

+117
-0
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4 files changed

+117
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lines changed

‎dist/sorting/quickSort.js

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"use strict";
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Object.defineProperty(exports, "__esModule", { value: true });
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function quickSort(arr, options = { direction: 'ascending' }, indexRange = [0, arr.length - 1]) {
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// TODO: add ability to pass cbFn as argument used to compare values, like js builtin sort
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const pivot = (arr, indexRange = [0, arr.length - 1]) => {
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const { direction } = options;
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const [startIndex, lastIndex] = indexRange;
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let matches = 0;
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let pivotIndex = startIndex; /* change pivotIndex selection to be more intentional,
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based on heuristics about the input array's median. */
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let pivotNum = arr[pivotIndex];
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for (let i = pivotIndex + 1; i <= lastIndex; i++) {
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if ((direction === 'ascending' && arr[i] < pivotNum)
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|| direction === 'descending' && arr[i] > pivotNum) {
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matches++;
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[arr[pivotIndex + matches], arr[i]] =
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[arr[i], arr[pivotIndex + matches]]; // swap matched num to be left of eventual pivot index
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}
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}
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[arr[pivotIndex], arr[pivotIndex + matches]] =
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[arr[pivotIndex + matches], arr[pivotIndex]]; // swap pivot into correct sorted position
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pivotIndex += matches;
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return pivotIndex;
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};
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let [left, right] = indexRange;
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let pivotIndex = pivot(arr, indexRange);
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if (pivotIndex - left > 1) {
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quickSort(arr, options, [left, pivotIndex - 1]);
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}
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if (right - pivotIndex > 1) {
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quickSort(arr, options, [pivotIndex + 1, right]);
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}
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return arr;
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}
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exports.default = quickSort;

‎dist/sorting/quickSort.test.js

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"use strict";
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var __importDefault = (this && this.__importDefault) || function (mod) {
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return (mod && mod.__esModule) ? mod : { "default": mod };
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};
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Object.defineProperty(exports, "__esModule", { value: true });
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const quickSort_1 = __importDefault(require("./quickSort"));
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let arr = [];
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beforeEach(() => arr = [5, 2, 1, 8, 4, 7, 6, 3]);
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describe('quicksort basic functionality', () => {
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test('quicksort exists', () => {
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expect(typeof quickSort_1.default).toBe('function');
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});
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test('quickSort returns same length array as it receives', () => {
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const originalLength = arr.length;
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expect(quickSort_1.default(arr).length).toBe(originalLength);
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});
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test('ascending: quicksort works on basic array', () => {
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quickSort_1.default(arr);
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expect(arr).toEqual([1, 2, 3, 4, 5, 6, 7, 8]);
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});
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test('descending: quicksort works on basic array', () => {
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quickSort_1.default(arr, { direction: 'descending' });
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expect(arr).toEqual([8, 7, 6, 5, 4, 3, 2, 1]);
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});
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});

‎src/sorting/quickSort.test.ts

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import quickSort from './quickSort';
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let arr: number[] = [];
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beforeEach(() => arr = [5, 2, 1, 8, 4, 7, 6, 3])
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describe('quicksort basic functionality', () => {
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test('quicksort exists', () => {
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expect(typeof quickSort).toBe('function');
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});
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test('quickSort returns same length array as it receives', () => {
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const originalLength = arr.length;
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expect(quickSort(arr).length).toBe(originalLength);
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});
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test('ascending: quicksort works on basic array', () => {
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quickSort(arr);
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expect(arr).toEqual([1, 2, 3, 4, 5, 6, 7, 8]);
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});
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test('descending: quicksort works on basic array', () => {
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quickSort(arr, { direction: 'descending' });
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expect(arr).toEqual([8, 7, 6, 5, 4, 3, 2, 1]);
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});
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})

‎src/sorting/quickSort.ts

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import SortOptions from './SortOptions';
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function quickSort<T>(arr: T[], options: SortOptions = { direction: 'ascending' }, indexRange: [number, number] = [0, arr.length - 1]): T[] {
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// TODO: add ability to pass cbFn as argument used to compare values, like js builtin sort
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const pivot = (arr: T[], indexRange: [number, number] = [0, arr.length - 1]): number => {
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const { direction } = options;
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const [startIndex, lastIndex] = indexRange;
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let matches = 0;
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let pivotIndex = startIndex; /* change pivotIndex selection to be more intentional,
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based on heuristics about the input array's median. */
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let pivotNum = arr[pivotIndex];
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for (let i = pivotIndex + 1; i <= lastIndex; i++) {
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if ((direction === 'ascending' && arr[i] < pivotNum)
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|| direction === 'descending' && arr[i] > pivotNum) {
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matches++;
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[arr[pivotIndex + matches], arr[i]] =
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[arr[i], arr[pivotIndex + matches]] // swap matched num to be left of eventual pivot index
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}
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}
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[arr[pivotIndex], arr[pivotIndex + matches]] =
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[arr[pivotIndex + matches], arr[pivotIndex]]; // swap pivot into correct sorted position
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pivotIndex += matches;
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return pivotIndex;
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}
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let [left, right] = indexRange;
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let pivotIndex = pivot(arr, indexRange);
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if (pivotIndex - left > 1) {
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quickSort(arr, options, [left, pivotIndex - 1]);
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}
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if (right - pivotIndex > 1) {
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quickSort(arr, options, [pivotIndex + 1, right]);
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}
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return arr;
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}
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export default quickSort;

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