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Add doctest on quickselect algorithm #625

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Jun 21, 2021
Merged

Add doctest on quickselect algorithm #625

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20 changes: 16 additions & 4 deletions Data-Structures/Array/QuickSelect.js
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Original file line number Diff line number Diff line change
Expand Up @@ -3,15 +3,19 @@
*
* Notes:
* -QuickSelect is related to QuickSort, thus has optimal best and average
* case (O(n)) but unlikely poor worst case (O(n^2))
* -case (O(n)) but unlikely poor worst case (O(n^2))
* -This implementation uses randomly selected pivots for better performance
*
* @complexity: O(n) (on average )
* @complexity: O(n^2) (worst case)
* @flow
*/

function QuickSelect (items, kth) {
function QuickSelect (items, kth) { // eslint-disable-line no-unused-vars
if (kth < 1 || kth > items.length) {
return 'Index Out of Bound'
}

return RandomizedSelect(items, 0, items.length - 1, kth)
}

Expand Down Expand Up @@ -62,5 +66,13 @@ function Swap (arr, x, y) {
[arr[x], arr[y]] = [arr[y], arr[x]]
}

// testing
console.log(QuickSelect([1, 4, 2, -2, 4, 5]))
// > QuickSelect([1, 4, 2, -2, 4, 5], 1)
// -2
// > QuickSelect([1, 4, 2, -2, 4, 5], 5)
// 4
// > QuickSelect([1, 4, 2, -2, 4, 5], 6)
// 5
// > QuickSelect([1, 4, 2, -2, 4, 5], 0)
// "Index Out of Bound"
// > QuickSelect([1, 4, 2, -2, 4, 5], 7)
// "Index Out of Bound"