mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-10-07 14:19:31 +00:00
47 lines
939 B
Python
47 lines
939 B
Python
"""
|
|
BFS.
|
|
|
|
pseudo-code:
|
|
|
|
BFS(graph G, start vertex s):
|
|
// all nodes initially unexplored
|
|
mark s as explored
|
|
let Q = queue data structure, initialized with s
|
|
while Q is non-empty:
|
|
remove the first node of Q, call it v
|
|
for each edge(v, w): // for w in graph[v]
|
|
if w unexplored:
|
|
mark w as explored
|
|
add w to Q (at the end)
|
|
|
|
"""
|
|
|
|
G = {
|
|
"A": ["B", "C"],
|
|
"B": ["A", "D", "E"],
|
|
"C": ["A", "F"],
|
|
"D": ["B"],
|
|
"E": ["B", "F"],
|
|
"F": ["C", "E"],
|
|
}
|
|
|
|
|
|
def bfs(graph, start):
|
|
"""
|
|
>>> ''.join(sorted(bfs(G, 'A')))
|
|
'ABCDEF'
|
|
"""
|
|
explored, queue = set(), [start] # collections.deque([start])
|
|
explored.add(start)
|
|
while queue:
|
|
v = queue.pop(0) # queue.popleft()
|
|
for w in graph[v]:
|
|
if w not in explored:
|
|
explored.add(w)
|
|
queue.append(w)
|
|
return explored
|
|
|
|
|
|
if __name__ == "__main__":
|
|
print(bfs(G, "A"))
|