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Welcome to the Merge Sort in Powershell page! Here, you'll find the source code for this program as well as a description of how the program works.
function Show-Usage() {
Write-Host 'Usage: please provide a list of at least two integers to sort in the format "1, 2, 3, 4, 5"'
Exit 1
}
function Parse-IntList([string]$Str) {
@($Str.Split(",") | ForEach-Object { [int]::Parse($_) })
}
# Source: https://en.wikipedia.org/wiki/Merge_sort#Top-down_implementation
function Invoke-MergeSort([array]$A) {
# Create temporary work array and copy the values into it
$B = @($A | ForEach-Object { $_ })
# Run the recursive merge sort
Invoke-MergeSortRec $A 0 $A.Length $B
}
function Invoke-MergeSortRec([array]$B, [int]$Lo, [int]$Hi, [array]$A) {
# Only sort if enough values
if (($Hi - $Lo) -gt 1) {
# Get midpoint
$Mid = ($Hi + $Lo) -shr 1
# Sort the left half (low to midpoint - 1) from A into B
Invoke-MergeSortRec $A $Lo $Mid $B
# Sort the right half (midpoint to high - 1) from A into B
Invoke-MergeSortRec $A $Mid $Hi $B
# Merge the two halves from B into A
Invoke-Merge $B $Lo $Mid $Hi $A
}
}
function Invoke-Merge([array]$B, [int]$Lo, [int]$Mid, [int]$Hi, [array]$A) {
$i = $Lo
$j = $Mid
# While there are elements in the left or right
for ($k = $Lo; $k -lt $Hi; $k++) {
# Copy the side that has the next largest value (or next available value if
# out of values) from the A into B
if ($i -lt $Mid -and ($j -ge $Hi -or $A[$i] -le $A[$j])) {
$B[$k] = $A[$i]
$i++
} else {
$B[$k] = $A[$j]
$j++
}
}
}
if ($args.Length -lt 1) {
Show-Usage
}
try {
$values = Parse-IntList $args[0]
if ($values.Length -lt 2) {
Show-Usage
}
} catch {
Show-Usage
}
Invoke-MergeSort $values
Write-Host ($values -join ', ')
Merge Sort in Powershell was written by:
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