PowerShell - sum-of-multiples

powershell/sum-of-multiples/SumOfMultiples.ps1

@@ -0,0 +1,36 @@
+Function Get-SumOfMultiples {
+    <#
+    .SYNOPSIS
+    Given a number, find the sum of all the unique multiples of particular numbers up to
+    but not including that number.
+
+    .DESCRIPTION
+    If we list all the natural numbers below 20 that are multiples of 3 or 5,
+    we get 3, 5, 6, 9, 10, 12, 15, and 18.
+
+    .PARAMETER Multiples
+    An array of the factors 
+
+    .PARAMETER Limit
+    The value BELOW which we test for
+
+    .EXAMPLE
+    Get-SumOfMultiples -Multiples @(3, 5) -Limit 10
+    
+    Returns 23
+    #>
+    [CmdletBinding()]
+    Param(
+        [int[]]$Multiples,
+        [int]$Limit
+    )
+
+    $set = @{}
+    foreach ($Multiple in $Multiples) {
+        if ($Multiple -gt $Limit) { continue }
+        [int] $Maximum = [Math]::Floor($Limit / $Multiple)
+        if ($Multiple * $Maximum -ge $Limit) { $Maximum -= 1 }
+        1..$Maximum | % { $set[$_ * $Multiple] = $true }
+    }
+    return ($set.Keys | Measure-Object -Sum).Sum 
+}