What is the largest n so that the following assertion is always true?
Assertion:
Let G be a graph with 10 vertices in which there is at least one edge among
any three vertices. Then G must contain Kn, where Kn is the complete graph
with n vertices.
请问为什么解答一开始就这么确定是K4, 然后就直接证是K4?
是要先用猜的吗? 还是有什么方法可以直接先判断是K4?