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 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 “” to “” (i.e. ). A pair of cards is called a “straight flush” if these two cards belong to the same suit and their ranks are adjacent. Additionally, "" and "" are considered to be adjacent (i.e. "A" is also considered as ""). For example, spade and spade form a “straight flush”; diamond and diamond 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.