def generate_random(nr_vertices, nr_edges=0):
if not 0 <= nr_edges <= nr_vertices * (nr_vertices - 1) / 2:
raise ValueError
if not nr_edges:
nr_edges = 0.5
graph = Graph()
graph.add(bits(*range(nr_vertices)))
if nr_edges < 1:
# Add random edges between groups
for v in graph:
for w in graph:
if v < w and random() < nr_edges:
graph.connect(v, w)
return graph
else:
vertex_list = list(iterate(graph.vertices))
for _ in range(nr_edges):
while 1:
v, w = sample(vertex_list, 2)
# Don't connect vertices twice
if not w in graph[v]:
break
graph.connect(v, w)
return graph
def __init__(self, grid_dict):
"""The grid is a 2d array of numbers."""
self.grid_dict = grid_dict
self.grid_matrix = dict_to_matrix(grid_dict)
for row in self.grid_matrix:
if len(row) != self.grid_width:
raise ValueError('Input grid is not a valid matrix.')
for val in row:
if val < 0:
raise ValueError('Input grid has negative numbers.')
# Detect fields by BFS
todo = [cell for cell in grid_dict]
fields = {} # Mapping from field number to group of cells
while todo:
front = [todo.pop()]
field = front[:]
current_number = grid_dict[field[0]]
if current_number in fields:
raise ValueError(
'Not all cells with the same number are in the same field'
)
while front:
current_cell = front.pop()
for neighbor_cell in neighbor_cells(grid_dict, current_cell):
if neighbor_cell in todo and grid_dict[neighbor_cell] == current_number:
front.append(neighbor_cell)
field.append(neighbor_cell)
todo.remove(neighbor_cell)
fields[current_number] = field
self.fields = fields
# Detect and create vertices
vertex_numbers = fields.keys()
vertices = bits(*vertex_numbers)
# Detect and create neighborhoods
neighborhoods = {}
for number, cells in fields.items():
neighbors = 0
for cell in cells:
for neighbor_cell in neighbor_cells(grid_dict, cell):
neighbors |= bit(grid_dict[neighbor_cell])
neighborhoods[bit(number)] = neighbors
Graph.__init__(self, vertices, neighborhoods)
