牛客網多校第五場 inv （思惟+逆序）

連接：https://www.nowcoder.com/acm/contest/143/D 來源：牛客網  c++ Kanade has an even number n and a permutation b of all of the even numbers in [1,n]數組 Let a denote an array [1,3,5....n-1] , now you need to f

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