Exercise (easy) : Prove that the edges of any planar graph $G$ can be oriented to obtain a directed graph $D$ so that the maximum out-degree in $D$ is bounded by five.
Exercise (relatively hard) : Prove that the edges of any planar graph $G$ can be oriented to obtain a directed graph $D$ so that the maximum out-degree in $D$ is bounded by three.
Posted: Jun 05 '12
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Last updated: Jun 07 '12
