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choose pivot from median of three elements for quicksort

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+17

-9

lines changed

src/algorithms/sorting/quick-sort
- QuickSort.js
- __test__
  - QuickSort.test.js

+17

-9

lines changed

Lines changed: 13 additions & 5 deletions

Original file line number	Diff line number	Diff line change
`@@ -14,13 +14,21 @@ export default class QuickSort extends Sort {`
`14`	`14`	`return array;`
`15`	`15`	`}`
`16`	`16`
`17`		`- // Init left and right arrays.`
	`17`	`+ // Init left, center, and right arrays.`
`18`	`18`	`const leftArray = [];`
`19`	`19`	`const rightArray = [];`
`20`		`-`
`21`		`- // Take the first element of array as a pivot.`
`22`		`- const pivotElement = array.shift();`
`23`		`- const centerArray = [pivotElement];`
	`20`	`+ const centerArray = [];`
	`21`	`+`
	`22`	`+ // Take the median element of first, mid, and last elements.`
	`23`	`+ let pivotElement = array[0];`
	`24`	`+ const mid = Math.floor(array.length / 2);`
	`25`	`+ if ((array[mid] < array[array.length - 1] && array[mid] > array[0])`
	`26`	`+ \|\| (array[mid] > array[array.length - 1] && array[mid] < array[0])) {`
	`27`	`+ pivotElement = array[mid];`
	`28`	`+ } else if ((array[array.length - 1] < array[mid] && array[array.length - 1] > array[0])`
	`29`	`+ \|\| (array[array.length - 1] > array[mid] && array[array.length - 1] < array[0])) {`
	`30`	`+ pivotElement = array[array.length - 1];`
	`31`	`+ }`
`24`	`32`
`25`	`33`	`// Split all array elements between left, center and right arrays.`
`26`	`34`	`while (array.length) {`

Lines changed: 4 additions & 4 deletions

Original file line number	Diff line number	Diff line change
`@@ -8,10 +8,10 @@ import {`
`8`	`8`	`} from '../../SortTester';`
`9`	`9`
`10`	`10`	`// Complexity constants.`
`11`		`-const SORTED_ARRAY_VISITING_COUNT = 190;`
`12`		`-const NOT_SORTED_ARRAY_VISITING_COUNT = 62;`
`13`		`-const REVERSE_SORTED_ARRAY_VISITING_COUNT = 190;`
`14`		`-const EQUAL_ARRAY_VISITING_COUNT = 19;`
	`11`	`+const SORTED_ARRAY_VISITING_COUNT = 66;`
	`12`	`+const NOT_SORTED_ARRAY_VISITING_COUNT = 83;`
	`13`	`+const REVERSE_SORTED_ARRAY_VISITING_COUNT = 66;`
	`14`	`+const EQUAL_ARRAY_VISITING_COUNT = 20;`
`15`	`15`
`16`	`16`	`describe('QuickSort', () => {`
`17`	`17`	`it('should sort array', () => {`

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