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optimized for loop & corrected comments (#617)

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The existing insertion sort implementation began by iterating from
0 until the end of the array, but it is only necessary to
iterate from 1 until the end of the array, since at the
0th index, there is nothing to compare to the left of
the element.

In order to complete this change, I also had to update the tests
to reflect the fact that the algorithm visits each index 1 less
time.

Finally, I corrected the grammar/wording of the comments.

Co-authored-by: Oleksii Trekhleb <trehleb@gmail.com>
This commit is contained in:
Austin Theriot 2021-01-03 03:26:14 -06:00 committed by GitHub
parent 81240342c2
commit cf61af59c5
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2 changed files with 7 additions and 7 deletions
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6
src/algorithms/sorting/insertion-sort/InsertionSort.js
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@ -5,14 +5,14 @@ export default class InsertionSort extends Sort {
const array = [...originalArray]; const array = [...originalArray];
// Go through all array elements... // Go through all array elements...
for (let i = 0; i < array.length; i += 1) { for (let i = 1; i < array.length; i += 1) {
let currentIndex = i; let currentIndex = i;
// Call visiting callback. // Call visiting callback.
this.callbacks.visitingCallback(array[i]); this.callbacks.visitingCallback(array[i]);
// Go and check if previous elements and greater then current one. // Check if previous element is greater than current element.
// If this is the case then swap that elements. // If so, swap the two elements.
while ( while (
array[currentIndex - 1] !== undefined array[currentIndex - 1] !== undefined
&& this.comparator.lessThan(array[currentIndex], array[currentIndex - 1]) && this.comparator.lessThan(array[currentIndex], array[currentIndex - 1])

8
src/algorithms/sorting/insertion-sort/__test__/InsertionSort.test.js
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@ -8,10 +8,10 @@ import {
} from '../../SortTester'; } from '../../SortTester';
// Complexity constants. // Complexity constants.
const SORTED_ARRAY_VISITING_COUNT = 20; const SORTED_ARRAY_VISITING_COUNT = 19;
const NOT_SORTED_ARRAY_VISITING_COUNT = 101; const NOT_SORTED_ARRAY_VISITING_COUNT = 100;
const REVERSE_SORTED_ARRAY_VISITING_COUNT = 210; const REVERSE_SORTED_ARRAY_VISITING_COUNT = 209;
const EQUAL_ARRAY_VISITING_COUNT = 20; const EQUAL_ARRAY_VISITING_COUNT = 19;
describe('InsertionSort', () => { describe('InsertionSort', () => {
it('should sort array', () => { it('should sort array', () => {