Find connected components of the complementary graph


You are given an undirected graph with $N$ vertices and $M$ edges.

Find all the connected components in the compliment of the given graph optimally (in $O(M)$ or $O(MlogN)$).

//input
4 4 //n,m
1 2 
1 3
4 2
4 3

//output
2 //no of connected components
2 1 4 
2 2 3 

Source

Editorial (I didn’t get it)