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C. Place for a Selfie The universe is a coordinate plane. There are $n$ space highways, each of which is a straight line $y=kx$ passing through the or 阅读全文
摘要:
D. A Wide, Wide Graph You are given a tree (a connected graph without cycles) with $n$ vertices. Consider a fixed integer $k$. Then, the graph $G_k$ i 阅读全文