Complete Graph ( Kn ) :-
Every node is adjacent to other node in the graph.
===> Degree of any node = n-1 , where n is no.of nodes.
Theorem :- Every Complete graph has a perfect matching iff no.of vertices is even
Why?
(Matching means 1 node can map atmost 1 node only) if no.of nodes=odd, one vertex should be can't match
What is i-regular graph?
every node degree = i in the graph ====> K(i+1) graph
For existing Perfect Matching i+1 should be even number.
given that 3-regular graph ===> 3+1 = 4 which is even ===> Has a perfect Matching.