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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 ] :
""" 廣度優先走訪 """
# 使用鄰接表來表示圖，以便獲取指定頂點的所有鄰接頂點
# 頂點走訪序列
res = [ ]
# 雜湊集合，用於記錄已被訪問過的頂點
visited = set [ Vertex ] ( [ start_vet ] )
# 佇列用於實現 BFS
que = deque [ Vertex ] ( [ start_vet ] )
# 以頂點 vet 為起點，迴圈直至訪問完所有頂點
while len ( que ) > 0 :
vet = que . popleft ( ) # 佇列首頂點出隊
res . append ( vet ) # 記錄訪問頂點
# 走訪該頂點的所有鄰接頂點
for adj_vet in graph . adj_list [ vet ] :
if adj_vet in visited :
continue # 跳過已被訪問的頂點
que . append ( adj_vet ) # 只入列未訪問的頂點
visited . add ( adj_vet ) # 標記該頂點已被訪問
# 返回頂點走訪序列
return res
""" Driver Code """
if __name__ == " __main__ " :
# 初始化無向圖
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 初始化後，圖為 " )
graph . print ( )
# 廣度優先走訪
res = graph_bfs ( graph , v [ 0 ] )
print ( " \n 廣度優先走訪（ ） " )
print ( vets_to_vals ( res ) )
