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In Action Problem Description Since 1945, when the first nuclear bomb was exploded by the Manhattan Project team in the US, the number of nuclear weap 阅读全文
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/* 数学是硬伤。。。。。。推了半小时推出来一个错误的公式 */ #include #include #include #include #define mod 1000000007 using namespace std; int n,t; /* 推出来的错误公式。。。。。。。 f[n]=f[n-1]+(n-1)*(f[n-1]-1); */ long long a[2000500];... 阅读全文
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Pseudoforest Problem Description In graph theory, a pseudoforest is an undirected graph in which every connected component has at most one cycle. The 阅读全文
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Connect the Cities Problem Description In 2100, since the sea level rise, most of the cities disappear. Though some survived cities are still connecte 阅读全文
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Jungle Roads Problem Description The Head Elder of the tropical island of Lagrishan has a problem. A burst of foreign aid money was spent on extra roa 阅读全文