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=begin
File: graph_bfs.rb
Created Time: 2024-04-25
Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
=end
require 'set'
require_relative './graph_adjacency_list'
require_relative '../utils/vertex'
### 广度优先遍历 ###
def graph_bfs ( graph , start_vet )
# 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 . new ( [ start_vet ] )
# 队列用于实现 BFS
que = [ start_vet ]
# 以顶点 vet 为起点，循环直至访问完所有顶点
while que . length > 0
vet = que . shift # 队首顶点出队
res << 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 ]
next if visited . include? ( adj_vet ) # 跳过已被访问的顶点
que << adj_vet # 只入队未访问的顶点
visited . add ( adj_vet ) # 标记该顶点已被访问
end
end
# 返回顶点遍历序列
res
end
### Driver Code ###
if __FILE__ == $0
# 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 . new ( edges )
puts " \n 初始化后，图为 "
graph . __print__
# 广度优先遍历
res = graph_bfs ( graph , v . first )
puts " \n 广度优先便利（ ） "
p vets_to_vals ( res )
end
