The graphs used in this problem are all sampled from an original graph with 4846609 nodes and 42851237 edges, for an average degree of about 17.7. You can download the examples from http://www.topcoder.com/contest/problem/Epidemic/examples.gz.

In the examples file, each line represents example (in order). If the line is scanned one integer at a time, where the funtion int() consumes the next integer on the line, the following code will produce the example graph:

    nodes = int();
    for(i = 0; i<nodes; i++){
        degree = int();
        for(j = 0; j<degree; j++){
            v = int();
            addEdge(i,v);
        }
    }

The C code used to sample the original graph can be downloaded from http://www.cs.cornell.edu/~lars/sample.c. The full dataset is now available for download. The first line in the file contains the degrees of all the nodes, in order. Each subsequent line contains the edge list for one node. For compactness, edges only appear in one edge list.