摘要：You are given a tetrahedron. Let's mark its vertices with letters A, B, C and D correspondingly. An ant is standing in the vertex D of the tetrahedron 阅读全文

摘要：Recently, Pari and Arya did some research about NP-Hard problems and they found the minimum vertex cover problem very interesting. Suppose the graph G 阅读全文

摘要：Daniel has a string s, consisting of lowercase English letters and period signs (characters '.'). Let's define the operation of replacement as the fol 阅读全文

摘要：output standard output output standard output output Ohana Matsumae is trying to clean a room, which is divided up into an n by n grid of squares. Eac 阅读全文

摘要：Permutation p is an ordered set of integers p1, p2, ..., pn, consisting of n distinct positive integers not larger than n. We'll denote as n the lengt 阅读全文