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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