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Ramesses knows a lot about problems involving trees (undirected connected graphs without cycles)! He created a new useful tree decomposition, but he d 阅读全文
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You are given a rooted tree with vertices numerated from 1 to n . A tree is a connected graph without cycles. A rooted tree has a special vertex named 阅读全文
摘要：
Consider a rooted tree. A rooted tree has one special vertex called the root. All edges are directed from the root. Vertex u is called a child of vert 阅读全文
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Party A company has n employees numbered from 1 to n. Each employee either has no immediate manager or exactly one immediate manager, who is another e 阅读全文