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"""
File: graph_bfs.py
Created Time: 2023-02-23
Author: krahets (krahets@163.com)
"""
import sys
from pathlib import Path
sys . path . append ( str ( Path ( __file__ ) . parent . parent ) )
from modules import Vertex , vals_to_vets , vets_to_vals
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 """
# 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 = [ ]
# 哈希集合，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
res = graph_bfs ( graph , v [ 0 ] )
print ( " \n 广度优先遍历（ ） " )
print ( vets_to_vals ( res ) )
