CSES Problem : Advanced Techniques Section
Is there a explanation and proof anyone can suggest me.
You are given an undirected graph that has n nodes and m edges.
We consider subgraphs that have all nodes of the original graph and some of its edges. A subgraph is called Eulerian if each node has even degree.
Your task is to count the number of Eulerian subgraphs modulo 109+7 .
Input
The first input line has two integers n and m : the number of nodes and edges. The nodes are numbered 1,2,…,n .
After this, there are m lines that describe the edges. Each line has two integers a and b : there is an edge between nodes a and b . There is at most one edge between two nodes, and each edge connects two distinct nodes.
