mirror of
https://github.com/fleschutz/PowerShell.git
synced 2024-11-28 19:03:49 +01:00
124 lines
4.1 KiB
Markdown
124 lines
4.1 KiB
Markdown
*measure-MergeSort.ps1*
|
|
================
|
|
|
|
This PowerShell script measures the speed of the MergeSort algorithm.
|
|
MergeSort is an efficient, general-purpose, and comparison-based sorting algorithm.
|
|
Most implementations produce a stable sort, which means that the order of equal elements
|
|
is the same in the input and output. Merge sort is a divide-and-conquer algorithm that
|
|
was invented by John von Neumann in 1945. A detailed description and analysis of bottom-up
|
|
merge sort appeared in a report by Goldstine and von Neumann as early as 1948.
|
|
|
|
Parameters
|
|
----------
|
|
```powershell
|
|
PS> ./measure-MergeSort.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
|
|
-------
|
|
```powershell
|
|
PS> ./measure-MergeSort.ps1
|
|
🧭 0.378 sec to sorting 1000 integers by MergeSort
|
|
|
|
```
|
|
|
|
Notes
|
|
-----
|
|
Author: Markus Fleschutz | License: CC0
|
|
|
|
Related Links
|
|
-------------
|
|
https://github.com/fleschutz/PowerShell
|
|
|
|
Script Content
|
|
--------------
|
|
```powershell
|
|
<#
|
|
.SYNOPSIS
|
|
Measures the speed of MergeSort
|
|
.DESCRIPTION
|
|
This PowerShell script measures the speed of the MergeSort algorithm.
|
|
MergeSort is an efficient, general-purpose, and comparison-based sorting algorithm.
|
|
Most implementations produce a stable sort, which means that the order of equal elements
|
|
is the same in the input and output. Merge sort is a divide-and-conquer algorithm that
|
|
was invented by John von Neumann in 1945. A detailed description and analysis of bottom-up
|
|
merge sort appeared in a report by Goldstine and von Neumann as early as 1948.
|
|
.PARAMETER numIntegers
|
|
Specifies the number of integers to sort
|
|
.EXAMPLE
|
|
PS> ./measure-MergeSort.ps1
|
|
🧭 0.378 sec to sorting 1000 integers by MergeSort
|
|
.LINK
|
|
https://github.com/fleschutz/PowerShell
|
|
.NOTES
|
|
Author: Markus Fleschutz | License: CC0
|
|
#>
|
|
|
|
param([int]$numIntegers = 1000)
|
|
|
|
class MergeSort {
|
|
|
|
static Merge($theArray, $tempArray, $leftPos, $rightPos, $rightEnd) {
|
|
$leftEnd = $rightPos - 1
|
|
$tmpPos = $leftPos
|
|
$numElements = $rightEnd - $leftPos + 1
|
|
|
|
while (($leftPos -le $leftEnd) -and ($rightPos -le $rightEnd)) {
|
|
if ($theArray[$leftPos].CompareTo($theArray[$rightPos]) -le 0) {
|
|
$tempArray[$tmpPos++] = $theArray[$leftPos++]
|
|
}
|
|
else {
|
|
$tempArray[$tmpPos++] = $theArray[$rightPos++]
|
|
}
|
|
}
|
|
|
|
while ($leftPos -le $leftEnd) { $tempArray[$tmpPos++] = $theArray[$leftPos++] }
|
|
while ($rightPos -le $rightEnd) { $tempArray[$tmpPos++] = $theArray[$rightPos++] }
|
|
|
|
for ($i = 0; $i -lt $numElements; $i++, $rightEnd--) {
|
|
$theArray[$rightEnd] = $tempArray[$rightEnd]
|
|
}
|
|
}
|
|
|
|
static Sort($theArray) {
|
|
$tempArray = New-Object Object[] $theArray.Count
|
|
[MergeSort]::Sort($theArray, $tempArray, 0, ($theArray.Count - 1))
|
|
}
|
|
|
|
static Sort($theArray, $tempArray, $left, $right) {
|
|
if ($left -lt $right) {
|
|
|
|
$center = [Math]::Floor(($left + $right) / 2)
|
|
|
|
[MergeSort]::Sort($theArray, $tempArray, $left, $center)
|
|
[MergeSort]::Sort($theArray, $tempArray, ($center + 1), $right)
|
|
|
|
[MergeSort]::Merge($theArray, $tempArray, $left, ($center + 1), $right)
|
|
}
|
|
}
|
|
}
|
|
|
|
$list = (1..$numIntegers | foreach{Get-Random -minimum 1 -maximum $numIntegers})
|
|
$stopWatch = [system.diagnostics.stopwatch]::startNew()
|
|
[MergeSort]::Sort($list)
|
|
[float]$elapsed = $stopWatch.Elapsed.TotalSeconds
|
|
$elapsed3 = "{0:N3}" -f $elapsed # formatted to 3 decimal places
|
|
"🧭 $elapsed3 sec to sort $numIntegers integers by MergeSort"
|
|
exit 0 # success
|
|
```
|
|
|
|
*(generated by convert-ps2md.ps1 using the comment-based help of measure-MergeSort.ps1 as of 12/07/2023 20:24:20)*
|