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75 lines
2.5 KiB
PowerShell
75 lines
2.5 KiB
PowerShell
<#
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.SYNOPSIS
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Measures the speed of HeapSort
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.DESCRIPTION
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This PowerShell script measures the speed of the HeapSort algorithm.
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HeapSort is a comparison-based sorting algorithm. Heapsort can be thought of as an
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improved selection sort: like selection sort, heapsort divides its input into a sorted
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and an unsorted region, and it iteratively shrinks the unsorted region by extracting
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the largest element from it and inserting it into the sorted region. Unlike selection
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sort, heapsort does not waste time with a linear-time scan of the unsorted region;
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rather, heap sort maintains the unsorted region in a heap data structure to more quickly
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find the largest element in each step.
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.PARAMETER numIntegers
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Specifies the number of integers to sort
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.EXAMPLE
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PS> ./measure-HeapSort.ps1
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🕒 HeapSort of 1000 integers took 0.6145732 sec
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.LINK
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https://github.com/fleschutz/PowerShell
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.NOTES
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Author: Markus Fleschutz | License: CC0
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#>
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param([int]$numIntegers = 1000)
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class HeapSort {
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static Sort($targetList) {
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$heapSize = $targetList.Count
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for ([int]$p = ($heapSize - 1) / 2; $p -ge 0; $p--) {
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[HeapSort]::MaxHeapify($targetList, $heapSize, $p)
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}
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for ($i = $targetList.Count - 1; $i -gt 0; $i--) {
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$temp = $targetList[$i]
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$targetList[$i] = $targetList[0]
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$targetList[0] = $temp
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$heapSize--
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[HeapSort]::MaxHeapify($targetList, $heapSize, 0)
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}
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}
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static MaxHeapify($targetList, $heapSize, $index) {
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$left = ($index + 1) * 2 - 1
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$right = ($index + 1) * 2
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$largest = 0
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if ($left -lt $heapSize -and $targetList[$left] -gt $targetList[$index]) {
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$largest = $left
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}
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else {
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$largest = $index
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}
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if ($right -lt $heapSize -and $targetList[$right] -gt $targetList[$largest]) {
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$largest = $right
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}
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if ($largest -ne $index) {
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$temp = $targetList[$index]
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$targetList[$index] = $targetList[$largest]
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$targetList[$largest] = $temp
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[HeapSort]::MaxHeapify($targetList, $heapSize, $largest)
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}
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}
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}
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$list = (1..$numIntegers | foreach{Get-Random -minimum 1 -maximum $numIntegers})
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$stopWatch = [system.diagnostics.stopwatch]::startNew()
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[HeapSort]::Sort($list)
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[float]$elapsed = $stopWatch.Elapsed.TotalSeconds
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"🕒 HeapSort of $numIntegers integers took $elapsed sec"
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exit 0 # success |