formatting the output of a .txt in powershell - powershell

Question

After a week of attempts I have to ask you this.
File input:
DD/MM
27,28
14,21
1
15
7
12
2,15
25
Each line of this file represents a month, so even if it´s empty, it should still count so the formatting can happen. Then based on file input, the desired output is:
Desired Output:
DD/MM
27/02
28/02
14/04
21/04
01/05
15/06
07/09
12/10
02/11
15/11
25/12
What I got so far and stuck here:
#getting the content into an array and formatting the .DAT file
$lines = Get-Content $outfileBR
If ($lines[0] -eq "DD/MM") {
$HEADER = $lines[0] + $linebreak
}
If ($lines[1] -eq '') {
continue
} Else {
$BRFILE = $lines[1].SUBSTRING(0,2) + "/01" + $linebreak
$BRFILE += $lines[1].SUBSTRING(3,2) + "/01" + $linebreak
}
If ($lines[2] -eq '') {
continue
} Else {
$BRFILE2 = $lines[2].SUBSTRING(0,2) + "/02" + $linebreak
$BRFILE2 += $lines[2].SUBSTRING(3,2) + "/02" + $linebreak
}
If ($lines[3] -eq '') {
continue
} Else {
$BRFILE3 = $lines[3].SUBSTRING(0,2) + "/03" + $linebreak
$BRFILE3 += $lines[3].SUBSTRING(3,2) + "/03" + $linebreak
}
Set-Content $BRdatFile ($HEADER + $BRFILE + $BRFILE2 + $BRFILE3)
Result:
DD/MM
/01
/01
27/02
28/02
/03
/03
Like I said, each line refers to a month, but if the line is empty (like shown in input file) I´ll not show it in the output. But on my result it´s appearing as /01 for January, /03 for march and so on.
What am I doing wrong, please?

Answer 1

Very similar to the answer given by Ronald Rink 'd-fens', I would do a loop within a loop, but since we know how many lines there should be in the file, I would do this:
#Get content of input file
$FileIn = Get-Content C:\Path\To\File.txt
#Start array for output with header record
[array]$FileOut += 'DD/MM'
#Loop 12 times, once for each month
ForEach($Month in (1..12)){
#Split the relevant line, and for each entry add a line to the output file
If([string]::IsNullOrEmpty($FileIn[$Month])){Continue}
$FileIn[$Month].Split(',') | ForEach{
$FileOut += '{0}/{1}' -f $_, $Month
}
}
#Output the new file
$FileOut | Set-Content C:\Path\To\NewFile.txt
Edit: I fixed 2 issues. I had [1..2] which should have been (1..12), and used the $_ reference instead of $Month (which should work anyway, but it's bad form imho).

Answer 2

Achieving this in PowerShell is as easy as this:
"DD/MM";
$lines = Get-Content $ENV:TEMP\input.txt;
for($c = 1; $c -lt $lines.Count; $c++)
{
$line = $lines[$c];
if(!$line) { continue; }
$line.Split(',') | % { '{0:00}/{1:00}' -f [int] $_, $c }
}
27/02
28/02
14/04
21/04
01/05
15/06
07/08
12/09
02/10
15/10
25/11
Edit: fixed $day/ $_