#!/usr/bin/ruby

# One digit is right and in its place
def rule_682(digits)
  correct = 0
  correct += 1 if digits[0] == 6
  correct += 1 if digits[1] == 8
  correct += 1 if digits[2] == 2
  return correct == 1
end

# One digit is right but in the wrong place
def rule_614(digits)
  correct = 0
  correct += 1 if (digits[1] == 6 || digits[2] == 6) && digits[0] != 6
  correct += 1 if (digits[0] == 1 || digits[2] == 1) && digits[1] != 1
  correct += 1 if (digits[0] == 4 || digits[1] == 4) && digits[2] != 4
  return correct == 1
end

# Two digits are right but both are in the wrong place
def rule_206(digits)
  correct = 0
  correct += 1 if (digits[1] == 2 || digits[2] == 2) && digits[0] != 2
  correct += 1 if (digits[0] == 0 || digits[2] == 0) && digits[1] != 0
  correct += 1 if (digits[0] == 6 || digits[1] == 6) && digits[2] != 6
  return correct == 2
end

# All digits are wrong
def rule_738(digits)
  wrong = [7, 3, 8]
  return false if wrong.include?(digits[0])
  return false if wrong.include?(digits[1])
  return false if wrong.include?(digits[1])
  return true
end

# One digit is right but in the wrong place
def rule_380(digits)
  correct = 0
  correct += 1 if (digits[1] == 3 || digits[2] == 3) && digits[0] != 3
  correct += 1 if (digits[0] == 8 || digits[2] == 8) && digits[1] != 8
  correct += 1 if (digits[0] == 0 || digits[1] == 0) && digits[2] != 0
  return correct == 1
end

for i in 0..999
  digits = []
  digits[0] = i / 100;
  digits[1] = (i / 10) % 10
  digits[2] = i % 10

  next if !rule_682(digits)
  next if !rule_614(digits)
  next if !rule_206(digits)
  next if !rule_738(digits)
  next if !rule_380(digits)

  puts digits.join()
end