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[组合] 每个由凸形状的国家组成的平面地图可用三种色染?

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isee posted 2017-9-15 16:37 |Read mode
证明或否定:每个由凸形状的国家组成的平面地图可以用三种颜色染色。

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abababa posted 2017-9-15 20:50
回复 1# isee
觉得是不能,比如下面这个图:
11.jpg

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original poster isee posted 2017-9-15 22:39
回复 2# abababa



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