Insertion sort script on powershell - algorithm

Question

I am trying to make insertion sort algorithm in case of studying on powershell.
Code:
$TestArrayList = [System.Collections.ArrayList]#(8, 2, 11, 12, 5, 6, 7)
for ($i = 0; $i -lt $TestArrayList.Count; $i++) {
$key = $TestArrayList[$i]
$j = $i-1
while($j -gt 0 -and $key -lt $TestArrayList[$j]){
$TestArrayList[$j+1] = $TestArrayList[$j]
$TestArrayList[$j] = $key
$j = $j-1
#Write-Output $TestArrayList[$i]
}
Write-Output $TestArrayList[$i]
}
Output of the code is next:
8
2
11
12
12
12
12
Can you please help me to analyze, what's the problem. I tried to make it sorted from small to bigger one.
Expected to be sorted:
2, 5, 6, 7, 8, 11, 12

Answer 1

There are two problems with your code right now:
The output is not the finally sorted list, it's intermediate output from the Write-Output statement.
There's an off-by-one bug in the nested while loop that'll cause the first item to always be ignored.
To fix the first issue, simply remove the Write-Output statement from the loop.
To fix the second issue, change the first comparison in the while condition to $j -ge 0 instead of $j -gt 0:
for ($i = 0; $i -lt $TestArrayList.Count; $i++) {
$key = $TestArrayList[$i]
$j = $i - 1
while($j -ge 0 -and $key -lt $TestArrayList[$j]){
$TestArrayList[$j+1] = $TestArrayList[$j]
$TestArrayList[$j] = $key
$j = $j - 1
}
}
# the list is now sorted correctly
$TestArrayList