/// <summary>
/// Returns a random simple graph containing <tt>V</tt> vertices and <tt>E</tt> edges.
/// </summary>
/// <param name="v">V the number of vertices</param>
/// <param name="e">E the number of edges</param>
/// <returns> random simple graph on <tt>V</tt> vertices, containing a total of <tt>E</tt> edges</returns>
/// <exception cref="ArgumentException">if no such simple graph exists</exception>
public static Graph Simple(int v, int e)
{
if (e > (long)v * (v - 1) / 2)
{
throw new ArgumentException("Too many edges");
}
if (e < 0)
{
throw new ArgumentException("Too few edges");
}
var g = new Graph(v);
var set = new SET <EdgeU>();
while (g.E < e)
{
var ve = StdRandom.Uniform(v);
var we = StdRandom.Uniform(v);
var edge = new EdgeU(ve, we);
if ((ve == we) || set.Contains(edge))
{
continue;
}
set.Add(edge);
g.AddEdge(ve, we);
}
return(g);
}
/// <summary>
/// Returns a random simple bipartite graph on <tt>V1</tt> and <tt>V2</tt> vertices
/// with <tt>E</tt> edges.
/// </summary>
/// <param name="v1">V1 the number of vertices in one partition</param>
/// <param name="v2">V2 the number of vertices in the other partition</param>
/// <param name="e">E the number of edges</param>
/// <returns>a random simple bipartite graph on <tt>V1</tt> and <tt>V2</tt> vertices, containing a total of <tt>E</tt> edges</returns>
/// <exception cref="ArgumentException">if no such simple bipartite graph exists</exception>
public static Graph Bipartite(int v1, int v2, int e)
{
if (e > (long)v1 * v2)
{
throw new ArgumentException("Too many edges");
}
if (e < 0)
{
throw new ArgumentException("Too few edges");
}
var g = new Graph(v1 + v2);
var vertices = new int[v1 + v2];
for (var i = 0; i < v1 + v2; i++)
{
vertices[i] = i;
}
StdRandom.Shuffle(vertices);
var set = new SET <EdgeU>();
while (g.E < e)
{
var i = StdRandom.Uniform(v1);
var j = v1 + StdRandom.Uniform(v2);
var edge = new EdgeU(vertices[i], vertices[j]);
if (set.Contains(edge))
{
continue;
}
set.Add(edge);
g.AddEdge(vertices[i], vertices[j]);
}
return(g);
}
