Please, merge my PowerShell examples for all chapters (#106)

* PowerShell 01_introduction_to_algorithms example

* PowerShell 02_selection_sort example

* PowerShell 03_recursion examples

* PowerShell 04_quicksort examples

* PowerShell 05_hash_tables examples

* PowerShell 06_breadth-first_search example

* PowerShell 07_dijkstras_algorithm example

* PowerShell 08_greedy_algorithms example

* Powershell 09_dynamic_programming example

04_quicksort/PowerShell/01_loop_sum.ps1

@@ -0,0 +1,12 @@
+function Get-GRKSum
+{
+    param($arr)
+    $total = 0
+    foreach ($x in $arr)
+    {
+        $total += $x
+    }
+    return $total
+}
+
+Get-GRKSum (1, 2, 3, 4)

04_quicksort/PowerShell/02_recursive_sum.ps1

@@ -0,0 +1,12 @@
+function Get-GRKSum
+{
+    param($list)
+    if ($list -eq $null)
+    {
+        return 0
+    }
+    return $list[0] + (Get-GRKSum ($list | Select-Object -Skip 1))
+
+}
+
+Get-GRKSum (1, 2, 3, 4)

04_quicksort/PowerShell/03_recursive_count.ps1

@@ -0,0 +1,11 @@
+function Get-GRKCount
+{
+    param($list)
+    if ($list -eq $null)
+    {
+        return 0
+    }
+    return 1 + (Get-GRKCount ($list | Select-Object -Skip 1))
+}
+
+Get-GRKCount ("one", "two", "three", "four")

04_quicksort/PowerShell/04_recursive_max.ps1

@@ -0,0 +1,27 @@
+function Get-GRKMax
+{
+    param($lst)
+    if ($lst.count -eq 0)
+    {
+        return $null
+    }
+    if ($lst.count -eq 1)
+    {
+        return $lst[0]
+    }
+    else
+    {
+        $sub_max = Get-GRKMax ($lst | Select-Object -Skip 1)
+        if ($lst[0] -gt $sub_max)
+        {
+            return $lst[0]
+        }
+        else
+        {
+            return $sub_max
+        }
+    }
+}
+
+
+Get-GRKMax (33, 7, 6, 100, 15, 13)

04_quicksort/PowerShell/05_quicksort.ps1

@@ -0,0 +1,28 @@
+function Get-GRKQuickSort
+{
+    param($array)
+    if ($array.count -lt 2)
+    {
+        # base case, arrays with 0 or 1 element are already "sorted"
+        if ($null -ne $array)
+        {
+            return , $array
+        }
+        else 
+        {
+            return $null
+        }
+    }
+    else
+    {
+        # recursive case
+        $pivot = $array[0]
+        # sub-array of all the elements less than the pivot
+        $less = @($array | Select-Object -Skip 1 | Where-Object {$_ -le $pivot})
+        # sub-array of all the elements greater than the pivot
+        $greater = @($array | Select-Object -Skip 1 | Where-Object {$_ -gt $pivot})
+        return @((Get-GRKQuickSort $less) + , $pivot + (Get-GRKQuickSort $greater))
+    }
+}
+
+Get-GRKQuickSort (5, 3, 6, 2, 10)