CF697E && CF696C PLEASE
題意：給你三個杯子，一開始鑰匙放在中間的杯子里，然后每一回合等概率將左右兩個杯子中的一個與中間杯子交換。求n回合之后鑰匙在中間杯子的概率。這里要求概率以分數形式輸出，先化成最簡，然后對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 推薦指數：
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