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文章目录题面分析代码题面洛谷P6030 [SDOI2012]走迷宫分析设dp[u]dp[u]dp[u]表示从uuu走到TTT的期望步数，VuV_uVu​表示uuu能到的点的集合，那么有dp[u]=∑v∈Vu1∣Vu∣⋅(dp[v]+1)=1∣Vu∣∑v∈vudp[v]+1\begin{aligned}dp[u]&=\sum\limits_{v\in V_u}\dfrac{1}{|...

文章目录题目题目大意分析代码题目DescriptionAgain, there are hard times in Berland! Many towns have such tensions that even civil war is possible.There are nnn towns in Reberland, some pairs of which connected by ...