My thoughts

来源: 于 2016-06-26 22:48:34 [博客] [旧帖] [给我悄悄话] 本文已被阅读：次

1. None of the dots can be at corner, since 2 dots cannot cover size 5 triangle.

2. We need one dot on every edge. Suppose there was no dot on the bottom edge, each dot can color 2 cells on the edge. 3 dots can cover 6 cells. But there are 7 cells on the edge.

3. Rotate triangle by 120 degrees and you get the same. So the solution is most likely symmetric.