jangkeng.rb

def jangkeng(you, comp)
  (you - comp + 4) % 3 - 1;
end

rock, paper, scissors = 0, 1, 2

win, lose, draw = 1, -1, 0

matches = [
  # [you, comp, judge]
  [rock, rock,     draw],
  [rock, scissors, win],
  [rock, paper,    lose],

  [paper, paper,    draw],
  [paper, rock,     win],
  [paper, scissors, lose],

  [scissors, scissors, draw],
  [scissors, paper,    win],
  [scissors, rock,     lose],
]

matches.map{|you, com, judge| jangkeng(you, com) == judge}.all? # => true