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feat: add dutchNationalFlagSort implementation #1305

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Mar 4, 2023
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1 change: 1 addition & 0 deletions DIRECTORY.md
Original file line number Diff line number Diff line change
Expand Up @@ -303,6 +303,7 @@
* [CombSort](Sorts/CombSort.js)
* [CountingSort](Sorts/CountingSort.js)
* [CycleSort](Sorts/CycleSort.js)
* [DutchNationalFlagSort](Sorts/DutchNationalFlagSort.js)
* [FindSecondLargestElement](Sorts/FindSecondLargestElement.js)
* [FisherYatesShuffle](Sorts/FisherYatesShuffle.js)
* [FlashSort](Sorts/FlashSort.js)
Expand Down
33 changes: 33 additions & 0 deletions Sorts/DutchNationalFlagSort.js
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/**
* @function dutchNationalFlagSort
* @description Dutch National Flag Sort is an algorithm to sort an array containing 0s, 1s, and 2s in linear time.
Time complexity of Dutch National Flag Sort Algorithm is O(n).
Auxiliary Space required for Dutch National Flag Sort Algorithm is O(1).
* @param {Integer[]} nums - Array of integers containing 0s, 1s, and 2s.
* @return {Integer[]} - Array of integers sorted in non-decreasing order.
* @see [Dutch National Flag Sort](https://en.wikipedia.org/wiki/Dutch_national_flag_problem)
*/
export function dutchNationalFlagSort (nums) {
let low = 0
let mid = 0
let high = nums.length - 1

while (mid <= high) {
switch (nums[mid]) {
case 0:
[nums[low], nums[mid]] = [nums[mid], nums[low]]
low++
mid++
break
case 1:
mid++
break
case 2:
[nums[mid], nums[high]] = [nums[high], nums[mid]]
high--
break
}
}

return nums
}
9 changes: 9 additions & 0 deletions Sorts/test/DutchNationalFlagSort.test.js
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import { dutchNationalFlagSort } from '../DutchNationalFlagSort'

describe('DutchNationalFlagSort', () => {
it('should sort arrays correctly', () => {
expect(dutchNationalFlagSort([2, 0, 2, 1, 1, 0])).toEqual([0, 0, 1, 1, 2, 2])
expect(dutchNationalFlagSort([2, 1, 0])).toEqual([0, 1, 2])
expect(dutchNationalFlagSort([1, 0, 0, 0, 1])).toEqual([0, 0, 0, 1, 1])
})
})