CF697E && CF696C PLEASE
题意：给你三个杯子，一开始钥匙放在中间的杯子里，然后每一回合等概率将左右两个杯子中的一个与中间杯子交换。求n回合之后钥匙在中间杯子的概率。这里要求概率以分数形式输出，先化成最简，然后对1e9 + 7取 ...
原文：CF696B Puzzles
Description Barney lives in country USC United States of Charzeh . USC has n cities numbered from through n and n roads between them. Cities and roads of USC form a rooted tree Barney s not sure why i ...
2018-10-08 10:24 0 857 推荐指数：
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