From 574113dff154d6d3897c7312eee2ce6b5a67abc7 Mon Sep 17 00:00:00 2001 From: Andrea Tota Date: Thu, 3 Mar 2022 18:38:50 +0100 Subject: [PATCH] Add alternative implementation for InsertionSort and relative test. Add additional algorithm description --- Sorts/InsertionSort.js | 51 ++++++++++++++++++++++++++++---- Sorts/test/InsertionSort.test.js | 19 ++++++++++++ 2 files changed, 65 insertions(+), 5 deletions(-) create mode 100644 Sorts/test/InsertionSort.test.js diff --git a/Sorts/InsertionSort.js b/Sorts/InsertionSort.js index a6f44dd93d..cf50df65fa 100644 --- a/Sorts/InsertionSort.js +++ b/Sorts/InsertionSort.js @@ -1,9 +1,10 @@ /* In insertion sort, we divide the initial unsorted array into two parts; -* sorted part and unsorted part. Initially the sorted part just has one -* element (Array of only 1 element is a sorted array). We then pick up -* element one by one from unsorted part; insert into the sorted part at -* the correct position and expand sorted part one element at a time. -*/ + * sorted part and unsorted part. Initially the sorted part just has one + * element (Array of only 1 element is a sorted array). We then pick up + * element one by one from unsorted part; insert into the sorted part at + * the correct position and expand sorted part one element at a time. + */ + export function insertionSort (unsortedList) { const len = unsortedList.length for (let i = 1; i < len; i++) { @@ -19,3 +20,43 @@ export function insertionSort (unsortedList) { unsortedList[j + 1] = tmp } } + +/** + * @function insertionSortAlternativeImplementation + * @description InsertionSort is a stable sorting algorithm + * @param {Integer[]} array - Array of integers + * @return {Integer[]} - Sorted array + * @see [InsertionSort](https://en.wikipedia.org/wiki/Quicksort) + */ + +/* + * Big-O Analysis + * Time Complexity + - O(N^2) on average and worst case scenario + - O(N) on best case scenario (when input array is already almost sorted) + * Space Complexity + - O(1) +*/ + +export function insertionSortAlternativeImplementation (array) { + const length = array.length + if (length < 2) return array + + for (let i = 1; i < length; i++) { + // Take current element in array + const currentItem = array[i] + // Take index of previous element in array + let j = i - 1 + + // While j >= 0 and previous element is greater than current element + while (j >= 0 && array[j] > currentItem) { + // Move previous, greater element towards the unsorted part + array[j + 1] = array[j] + j-- + } + // Insert currentItem number at the correct position in sorted part. + array[j + 1] = currentItem + } + // Return array sorted in ascending order + return array +} diff --git a/Sorts/test/InsertionSort.test.js b/Sorts/test/InsertionSort.test.js new file mode 100644 index 0000000000..6a35e83561 --- /dev/null +++ b/Sorts/test/InsertionSort.test.js @@ -0,0 +1,19 @@ +import { insertionSortAlternativeImplementation } from '../InsertionSort' + +describe('insertionSortAlternativeImplementation', () => { + it('expects to work with empty array', () => { + expect(insertionSortAlternativeImplementation([])).toEqual([]) + }) + + it('expects to return input array when array.length is less than 2', () => { + const input = [3] + expect(insertionSortAlternativeImplementation(input)).toEqual(input) + }) + + it('expects to return array sorted in ascending order', () => { + expect(insertionSortAlternativeImplementation([14, 11])).toEqual([11, 14]) + expect(insertionSortAlternativeImplementation([21, 22, 23])).toEqual([21, 22, 23]) + expect(insertionSortAlternativeImplementation([1, 3, 2, 3, 7, 2])).toEqual([1, 2, 2, 3, 3, 7]) + expect(insertionSortAlternativeImplementation([1, 6, 4, 5, 9, 2])).toEqual([1, 2, 4, 5, 6, 9]) + }) +}) pFad - Phonifier reborn

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