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。。。懒得说什么了 阅读全文
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Jimmy experiences a lot of stress at work these days, especially since his accident made working difficult. To relax after a hard day, he likes to wal 阅读全文
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The math department has been having problems lately. Due to immense amount of unsolicited automated programs which were crawling across their pages, t 阅读全文
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题意:T组数据,给次给出N,M,K,多少种方案,用[0,N-1]范围的数,表示一个M排列,其和为K; 思路:隔板法,不限制[0,N-1]的时候答案是C(M+K-1,M-1);那么我们减去至少一个>=N,加上至少两个>=N....即可得到答案。 假设至少一个隔板里的数大于大于N,我们从这个隔板里抽出N 阅读全文