摘要：The computer op erates on a single stack of sets, which is initially empty. After each op eration, thecardinality of the topmost set on the stack is o... 阅读全文

摘要：Most crossword puzzle fans are used toanagrams--groups of words with the same letters in different orders--for example OPTS, SPOT, STOP, POTS and POST... 阅读全文