single_char_edit_complete.rb

def single_char_edit?(a, b)
  if a.size == b.size
    diffs = 0

    a.size.times do |i|
      if a[i] != b[i]
        diffs += 1
      end
    end

    diffs == 1
  elsif (a.size - b.size).abs == 1
    long = a
    short = b

    if b.size > a.size
      long = b
      short = a
    end

    diffs = 0

    short.size.times do |i|
      if short[i] != long[i + diffs]
        diffs += 1

        if diffs > 1
          break
        end
      end
    end

    if diffs.zero?
      diffs = 1 # for the length difference
    end

    diffs == 1
  else
    false
  end
end

def check(a, b, expected)
  if single_char_edit?(a, b) == expected
    puts "OK #{a.inspect}, #{b.inspect} = #{expected}"
    true
  else
    puts "FAIL #{a.inspect}, #{b.inspect}, expected to eq #{expected}"
    false
  end
end

def test_suite
  res = [
    check("abc", "ab", true),
    check("abc", "abe", true),
    check("abc", "abc", false),
    check("abc", "bb", false),
    check("abc", "ABc", false),
    check("123", "32", false),
    check("1234", "134", true),
  ]

  if res.all?
    puts '... Complete sucess! ...'
  end
end