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Adds Floyd Warshall Algorithm

pull/33/head
Pulkit Mishra GitHub 1 year ago
parent
commit
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1 changed files with 142 additions and 0 deletions
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      graphing/floyd_warshall.py

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graphing/floyd_warshall.py View File

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class Graph:
def __init__(self):
self.vertices = {}
def add_vertex(self, key):
vertex = Vertex(key)
self.vertices[key] = vertex
def get_vertex(self, key):
return self.vertices[key]
def __contains__(self, key):
return key in self.vertices
def add_edge(self, src_key, dest_key, weight=1):
self.vertices[src_key].add_neighbour(self.vertices[dest_key], weight)
def does_edge_exist(self, src_key, dest_key):
return self.vertices[src_key].does_it_point_to(self.vertices[dest_key])
def __len__(self):
return len(self.vertices)
def __iter__(self):
return iter(self.vertices.values())
class Vertex:
def __init__(self, key):
self.key = key
self.points_to = {}
def get_key(self):
return self.key
def add_neighbour(self, dest, weight):
self.points_to[dest] = weight
def get_neighbours(self):
return self.points_to.keys()
def get_weight(self, dest):
return self.points_to[dest]
def does_it_point_to(self, dest):
return dest in self.points_to
def floyd_warshall(g):
distance = {v:dict.fromkeys(g, float('inf')) for v in g}
next_v = {v:dict.fromkeys(g, None) for v in g}
for v in g:
for n in v.get_neighbours():
distance[v][n] = v.get_weight(n)
next_v[v][n] = n
for v in g:
distance[v][v] = 0
next_v[v][v] = None
for p in g:
for v in g:
for w in g:
if distance[v][w] > distance[v][p] + distance[p][w]:
distance[v][w] = distance[v][p] + distance[p][w]
next_v[v][w] = next_v[v][p]
return distance, next_v
def print_path(next_v, u, v):
p = u
while (next_v[p][v]):
print('{} -> '.format(p.get_key()), end='')
p = next_v[p][v]
print('{} '.format(v.get_key()), end='')
g = Graph()
print('Menu')
print('add vertex <key>')
print('add edge <src> <dest> <weight>')
print('floyd-warshall')
print('display')
print('quit')
while True:
do = input('What would you like to do? ').split()
operation = do[0]
if operation == 'add':
suboperation = do[1]
if suboperation == 'vertex':
key = int(do[2])
if key not in g:
g.add_vertex(key)
else:
print('Vertex already exists.')
elif suboperation == 'edge':
src = int(do[2])
dest = int(do[3])
weight = int(do[4])
if src not in g:
print('Vertex {} does not exist.'.format(src))
elif dest not in g:
print('Vertex {} does not exist.'.format(dest))
else:
if not g.does_edge_exist(src, dest):
g.add_edge(src, dest, weight)
else:
print('Edge already exists.')
elif operation == 'floyd-warshall':
distance, next_v = floyd_warshall(g)
print('Shortest distances:')
for start in g:
for end in g:
if next_v[start][end]:
print('From {} to {}: '.format(start.get_key(),
end.get_key()),
end = '')
print_path(next_v, start, end)
print('(distance {})'.format(distance[start][end]))
elif operation == 'display':
print('Vertices: ', end='')
for v in g:
print(v.get_key(), end=' ')
print()
print('Edges: ')
for v in g:
for dest in v.get_neighbours():
w = v.get_weight(dest)
print('(src={}, dest={}, weight={}) '.format(v.get_key(),
dest.get_key(), w))
print()
elif operation == 'quit':
break

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