有一棵树，树上有只毛毛虫。它在这棵树上生活了很久，对它的构造了如指掌。所以它在树上从来都是走最短路，不会绕路。它还还特别喜欢三角形，所以当它在树上爬来爬去的时候总会在想，如果把刚才爬过的那几根树枝/树干锯下来，能不能从中选三根出来拼成一个三角形呢？-A tree, a tree caterpillar. It in the tree of life for a long time, it constructed well aware. In the trees, it has always been to go the shortest path, not a detour. It is also particularly like the triangle, so when it was crawling around in the trees always thinking, if just climbed a few branches/trunk sawed off, you can select from three out makes up a triangle ?