Question

Let G be a graph which is self complimentary. (G=Gbar)
Let |V| be the number of vertices of G (and therefore of Gbar)
Prove that |V| = 0mod[4]or |V|=1mod[4]
the = signs has 3bars (respect to modulo notation)
Smarties help please

Answer 1

I got it, if you stop by , please check. Smarties!!
by definition of self-complimentary graph, with n vertices, the graph must have n(n-1)/ 4 edges. That means n or n -1 must be divisible by 4 ---> which implies 4|n or 4|n-1 . In other words, n = 0mod[4] or n =1mod[4]