Three-colouring arrangements of great circles
Prove that the crossing points of every simple arrangement of great circles can be 3-coloured, or find one that needs four colours.
Issue
疑问、子问题和求助。把大问题拆成子 Issue;从任何一个 Issue 都能开出路线。
没有已关闭的 Issue
Issue 用来放疑问、子问题和求助。