mirror of
https://github.com/krahets/hello-algo.git
synced 2024-12-27 04:56:29 +08:00
63 lines
1.8 KiB
Python
63 lines
1.8 KiB
Python
"""
|
||
File: graph_bfs.py
|
||
Created Time: 2023-02-23
|
||
Author: Krahets (krahets@163.com)
|
||
"""
|
||
|
||
import sys, os.path as osp
|
||
|
||
sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
|
||
from modules import *
|
||
from collections import deque
|
||
from graph_adjacency_list import GraphAdjList
|
||
|
||
|
||
def graph_bfs(graph: GraphAdjList, start_vet: Vertex) -> list[Vertex]:
|
||
"""广度优先遍历 BFS"""
|
||
# 使用邻接表来表示图，以便获取指定顶点的所有邻接顶点
|
||
# 顶点遍历序列
|
||
res = []
|
||
# 哈希表，用于记录已被访问过的顶点
|
||
visited = set[Vertex]([start_vet])
|
||
# 队列用于实现 BFS
|
||
que = deque[Vertex]([start_vet])
|
||
# 以顶点 vet 为起点，循环直至访问完所有顶点
|
||
while len(que) > 0:
|
||
vet = que.popleft() # 队首顶点出队
|
||
res.append(vet) # 记录访问顶点
|
||
# 遍历该顶点的所有邻接顶点
|
||
for adj_vet in graph.adj_list[vet]:
|
||
if adj_vet in visited:
|
||
continue # 跳过已被访问过的顶点
|
||
que.append(adj_vet) # 只入队未访问的顶点
|
||
visited.add(adj_vet) # 标记该顶点已被访问
|
||
# 返回顶点遍历序列
|
||
return res
|
||
|
||
|
||
"""Driver Code"""
|
||
if __name__ == "__main__":
|
||
# 初始化无向图
|
||
v = vals_to_vets([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
|
||
edges = [
|
||
[v[0], v[1]],
|
||
[v[0], v[3]],
|
||
[v[1], v[2]],
|
||
[v[1], v[4]],
|
||
[v[2], v[5]],
|
||
[v[3], v[4]],
|
||
[v[3], v[6]],
|
||
[v[4], v[5]],
|
||
[v[4], v[7]],
|
||
[v[5], v[8]],
|
||
[v[6], v[7]],
|
||
[v[7], v[8]],
|
||
]
|
||
graph = GraphAdjList(edges)
|
||
print("\n初始化后，图为")
|
||
graph.print()
|
||
|
||
# 广度优先遍历 BFS
|
||
res = graph_bfs(graph, v[0])
|
||
print("\n广度优先遍历（BFS）顶点序列为")
|
||
print(vets_to_vals(res))
|