I have the following array and need two Regex filters that I want to use in PowerShell.

000111
010101
220220
123456

Filter 1: the number 0 that occurs equal or more than three times. I expect the following values after filtering

000111
010101

Filter 2: all numbers that occur equal or more than three times. I should only see these numbers.

000111
010101
220220

With 0{3,} I can only recognize numbers in sequence so i get only the number

000111

Is it possible to find repeating numbers that are between other numbers?

CodePudding user response：

If using just a regex pattern for each filter is even possible, it will likely be mind-bending (hard to understand).
Either way, you can use additional PowerShell features to achieve the desired results in a conceptually clear manner:

Filter 1:

@(
  '000111'
  '010101'
  '220220'
  '123456'
).Where({ ($_ -replace '[^0]').Length -ge 3 })

That is, each string in the input array (enumerated via the intrinsic Where() method), has all chars. that aren't '0' ([^0]) removed via the regex-based -replace operator, and only those strings for which the resulting string has 3 or more characters, i.e. '0' instances, are returned.

Filter 2:

@(
  '000111'
  '010101'
  '220220'
  '123456'
).Where({ ([char[]] $_ | Group-Object).Where({ $_.Count -ge 3 }, 'First') })

That is, each input string by is grouped by its characters using Group-Object, and only those groups comprising at least 3 members are considered, with the first such group being found ('First') stopping the search for further groups.
If a group is returned, the enclosing .Where() method call will include the string at hand in the output, based on PowerShell's implicit to-Boolean conversion rules, which are summarized in the bottom section of this answer.

CodePudding user response：

Since you insist to see the solution in regex, look at this: '(\d).*\1.*\1'

I think this is comprehensible without further explanation, isn't it?