Ruby: How to replace odd/even occurrences in a string

input = AA-AA-AA-AA-AA-AA

How do I

  • Replace odd (1st, 3rd, 5th) occurrence with :
  • Replace even (2nd, 4th) occurrence with .

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  • 4 Solutions collect form web for “Ruby: How to replace odd/even occurrences in a string”

    input.gsub("-").with_index(1){|_, i| i.odd? ? ":" : "."}
    # => "AA:AA.AA:AA.AA:AA"

    Here’s one way, although its not the one-liner you’re probably looking for:

    input = 'AA-AA-AA-AA-AA-AA'
    input.count('-').times do |i|
      replacement = i.even? ? ':' : '.'
      input.sub!('-', replacement)
    # => "AA:AA.AA:AA.AA:AA"
    input = "AA-AA-AA-AA-AA-AA".gsub("AA-AA", ":-.")


    count= 0
    input.gsub!(/\-/) do |s|
      count+= 1; s= count% 2== 0 ? '.' : ':'
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