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题面:https://www.luogu.org/problem/P3106 cpp 首先以n为起点两边spfa，之后再判断所有的边是否在最短路上，以警告次数作为边权再次spfa. Code: include include include include include include using 阅读全文
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题面:https://www.luogu.org/problem/P4009 cpp 分层图,建k+1层分别表示满油到没油,然后根据当前点是否有加油站在层间建边即可. Code: include include include include include include using namesp 阅读全文
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```cpp 【题目描述】 原题来自：USACO 2009 Feb. Silver 牡 mǔ，畜父也。牝 pìn，畜母也。 ——《说文解字》 约翰要带 N 只牛去参加集会里的展示活动，这些牛可以是牡牛，也可以是牝牛。牛们要站成一排，但是牡牛是好斗的，为了避免牡牛闹出乱子，约翰决定任意两只牡牛之间至少 阅读全文
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```cpp include include include include include include include include using namespace std; const int N=100005; int n,m,p; long long A[N+5],B[N+5]; in 阅读全文