摘要：
At the beginning of every day, the first person who signs in the computer room will unlock the door, and the last one who signs out will lock the door 阅读全文
摘要：
With the 2010 FIFA World Cup running, football fans the world over were becoming increasingly excited as the best players from the best teams doing ba 阅读全文
摘要：
The highest building in our city has only one elevator. A request list is made up with N positive numbers. The numbers denote at which floors the elev 阅读全文