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链接：http://acm.hdu.edu.cn/showproblem.php?pid=6331 Walking Plan Problem Description There are n intersections in Bytetown, connected with m one way str 阅读全文
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链接：http://acm.hdu.edu.cn/showproblem.php?pid=6325 Interstellar Travel Problem Description After trying hard for many years, Little Q has finally recei 阅读全文
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Little Q and Little T are playing a game on a tree. There are n vertices on the tree, labeled by 1,2,...,n , connected by n−1 bidirectional edges. The 阅读全文
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链接：http://acm.hdu.edu.cn/showproblem.php?pid=6322 Problem Description In number theory, Euler's totient function φ(n) counts the positive integers up 阅读全文