2020牛客暑期多校訓練營（第六場）——K K-Bag

2020牛客暑期多校訓練營（第六場）——K K-Bag 題目描述 A sequence is called kk-bag, if and only if it is put in order by some (maybe one) permutations of 1 to k. For example, 1,2,3,2,1,3,3,2,1 is a valid 33-bag sequence. R

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