PowerShell/docs/measure-CountingSort.md

measure-CountingSort.ps1

This PowerShell script measures the speed of the CountingSort algorithm. CountingSort is an algorithm for sorting a collection of objects according to keys that are small positive integers; that is, it is an integer sorting algorithm. It operates by counting the number of objects that possess distinct key values, and applying prefix sum on those counts to determine the positions of each key value in the output sequence. Its running time is linear in the number of items and the difference between the maximum key value and the minimum key value, so it is only suitable for direct use in situations where the variation in keys is not significantly greater than the number of items. It is often used as a subroutine in radix sort, another sorting algorithm, which can handle larger keys more efficiently.

Parameters

PS> ./measure-CountingSort.ps1 [[-numIntegers] <Int32>] [<CommonParameters>]

-numIntegers <Int32>
    Specifies the number of integers to sort
    
    Required?                    false
    Position?                    1
    Default value                1000
    Accept pipeline input?       false
    Accept wildcard characters?  false

[<CommonParameters>]
    This script supports the common parameters: Verbose, Debug, ErrorAction, ErrorVariable, WarningAction, 
    WarningVariable, OutBuffer, PipelineVariable, and OutVariable.

Example

PS> ./measure-CountingSort.ps1
🧭 0.045 sec to sort 1000 integers by CountingSort

Notes

Author: Markus Fleschutz | License: CC0

Related Links

https://github.com/fleschutz/PowerShell

Script Content

<#
.SYNOPSIS
        Measures the speed of CountingSort
.DESCRIPTION
        This PowerShell script measures the speed of the CountingSort algorithm.
        CountingSort is an algorithm for sorting a collection of objects according to keys
	that are small positive integers; that is, it is an integer sorting algorithm. It
	operates by counting the number of objects that possess distinct key values, and
	applying prefix sum on those counts to determine the positions of each key value in
	the output sequence. Its running time is linear in the number of items and the difference
	between the maximum key value and the minimum key value, so it is only suitable for direct
	use in situations where the variation in keys is not significantly greater than the number
	of items. It is often used as a subroutine in radix sort, another sorting algorithm, which
	can handle larger keys more efficiently.
.PARAMETER numIntegers
        Specifies the number of integers to sort
.EXAMPLE
        PS> ./measure-CountingSort.ps1
        🧭 0.045 sec to sort 1000 integers by CountingSort 
.LINK
        https://github.com/fleschutz/PowerShell
.NOTES
        Author: Markus Fleschutz | License: CC0
#>

param([int]$numIntegers = 1000)

class CountingSort {
    static Sort($targetList) {
        $min = 0
        $max = 0

        for ($counter = 0; $counter -lt $targetList.Count; $counter++) {
            if ($targetList[$counter] -lt $min) { $min = $targetList[$counter] }
            if ($targetList[$counter] -gt $max) { $max = $targetList[$counter] }
        }

        $arrayBucket = New-Object int[] ($max - $min + 1)

        for ($counter = 0; $counter -lt $targetList.Count; $counter++) {
            $arrayBucket[$targetList[$counter]]++;
        }

        $lastPosition = 0
        for ($counter = 0; $counter -lt $arrayBucket.Count ; $counter++) {
            for ($innerCounter = 0; $innerCounter -lt $arrayBucket[$counter]; $innerCounter++) {
                $targetList[$lastPosition++] = $counter
            }
        }
    }
}

$list = (1..$numIntegers | foreach{Get-Random -minimum 1 -maximum $numIntegers})
$stopWatch = [system.diagnostics.stopwatch]::startNew()
[CountingSort]::Sort($list)
[float]$elapsed = $stopWatch.Elapsed.TotalSeconds
$elapsed3 = "{0:N3}" -f $elapsed # formatted to 3 decimal places
"🧭 $elapsed3 sec to sort $numIntegers integers by CountingSort"
exit 0 # success

(generated by convert-ps2md.ps1 using the comment-based help of measure-CountingSort.ps1 as of 01/03/2024 12:10:49)