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摘要： Key SetProblem Descriptionsoda has a set S with n integers {1,2,…,n}. A set is called key set if the sum of integers in the set is an even number. He ... 阅读全文

摘要： UntitledProblem DescriptionThere is an integer a and n integers b1,…,bn. After selecting some numbers from b1,…,bn in any order, say ... 阅读全文

摘要： Power Strings Description Given two strings a and b we define a*b to be their concatenation. For example, if a = "abc" and b = "def" then a*b = "abcde 阅读全文