Three of a kind, also called trips or a set, is a poker hand such as 2♦ 2♠ 2♣ K♠ 6♥ that contains three cards of the same rank, plus two cards which are not of this rank nor the same as each other.
http://en.wikipedia.org/wiki/List_of_poker_hands#Three_of_a_kind
更新1:
why 13C1 x 4C2 x 12C1 x 4C1 x 11C1 x 4C1 is wrong ?
