def bipartite(V1, V2, E):
'''
* Returns a random simple bipartite graph on V1 and V2 vertices
* with E edges.
* @param V1 the number of vertices in one partition
* @param V2 the number of vertices in the other partition
* @param E the number of edges
* @return a random simple bipartite graph on V1 and V2 vertices,
* containing a total of E edges
* @raises ValueError if no such simple bipartite graph exists
'''
if E > V1 * V2:
raise ValueError('Too many edges')
if E < 0:
raise ValueError('Too few edges')
# Modification question #5
if V1 < 0 or V2 < 0:
raise ValueError("Vertex value cannot be less then 0")
G = Graph(V1 + V2)
vertices = [i for i in range(V1 + V2)]
rand.shuffle(vertices)
edges = []
while G.E() < E:
i = rand.randrange(V1)
j = V1 + rand.randrange(V2)
e = (vertices[i], vertices[j])
if e not in edges:
edges.append(e)
G.add_edge(e)
return G
def simple(V, E):
'''
Returns a random simple graph containing V vertices and E edges.
@param V the number of vertices
@param E the number of edges
@return a random simple graph on V vertices, containing a total of E edges
@raises ValueError if no such simple graph exists
'''
if E > V * (V - 1) / 2:
raise ValueError("Too many edges")
if E < 0:
raise ValueError("Too few edges")
# Modification question #5
if V <= 0:
raise ValueError("A simple graph must have at least one vertex")
G = Graph(V)
edges = []
while G.E() < E:
v = rand.randrange(V)
w = rand.randrange(V)
e = (v, w)
if v != w and e not in edges:
edges.append(e)
G.add_edge(e)
return G