摘要：
Broken NecklaceYou have a necklace of N red, white, or blue beads (3<=N<=350) some of which are red, others blue, and others white, arranged at random. Here are two examples for n=29: The beads ... 阅读全文
摘要：
Friday the ThirteenthIs Friday the 13th really an unusual event? That is, does the 13th of the month land on a Friday less often than on any other day of the week? To answer this question, write a pro... 阅读全文