MathDB
problem of playing cards

Source: China south east mathematical olympiad 2006 day1 problem 3

July 4, 2013
algorithmgeometrygeometric transformationcombinatorics unsolvedcombinatorics

Problem Statement

There is a standard deck of 5252 cards without jokers. The deck consists of four suits(diamond, club, heart, spade) which include thirteen cards in each. For each suit, all thirteen cards are ranked from “22” to “AA” (i.e. 2,3,,Q,K,A2, 3,\ldots , Q, K, A). A pair of cards is called a “straight flush” if these two cards belong to the same suit and their ranks are adjacent. Additionally, "AA" and "22" are considered to be adjacent (i.e. "A" is also considered as "11"). For example, spade AA and spade 22 form a “straight flush”; diamond 1010 and diamond QQ are not a “straight flush” pair. Determine how many ways of picking thirteen cards out of the deck such that all ranks are included but no “straight flush” exists in them.