Set

Set is a card game played with a deck of 81 unique cards that vary in four features, each of which take on three values:

• Number of shapes: each card contains either 1, 2, or 3 shapes.
• Color: the shapes on each card are either Red, Green, or Purple.
• Shading: each shape is either Solid, Half-shaded, or Empty.
• Shape: the shapes on each card are either Ovals, Diamonds, or Waves.

The goal of the game is to find a set of three cards, such that for each of the four features, either all three cards have different values or all three cards have the same value.

Each card is represented by the values of its features, with each value encoded by the first character. For example, 2RSW means 2 Red Solid Waves.

Each argument represents twelve cards that are laid out. In order of appearance, print the three cards that make up each set per argument on the same line, separated by spaces.

External links: Rosetta Code, Wikipedia