You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
65 lines
1.9 KiB
65 lines
1.9 KiB
"""
|
|
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]:
|
|
"""Breadth-first traversal"""
|
|
# Use adjacency list to represent the graph, to obtain all adjacent vertices of a specified vertex
|
|
# Vertex traversal sequence
|
|
res = []
|
|
# Hash set, used to record visited vertices
|
|
visited = set[Vertex]([start_vet])
|
|
# Queue used to implement BFS
|
|
que = deque[Vertex]([start_vet])
|
|
# Starting from vertex vet, loop until all vertices are visited
|
|
while len(que) > 0:
|
|
vet = que.popleft() # Dequeue the vertex at the head of the queue
|
|
res.append(vet) # Record visited vertex
|
|
# Traverse all adjacent vertices of that vertex
|
|
for adj_vet in graph.adj_list[vet]:
|
|
if adj_vet in visited:
|
|
continue # Skip already visited vertices
|
|
que.append(adj_vet) # Only enqueue unvisited vertices
|
|
visited.add(adj_vet) # Mark the vertex as visited
|
|
# Return the vertex traversal sequence
|
|
return res
|
|
|
|
|
|
"""Driver Code"""
|
|
if __name__ == "__main__":
|
|
# Initialize undirected graph
|
|
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("\nAfter initialization, the graph is")
|
|
graph.print()
|
|
|
|
# Breadth-first traversal
|
|
res = graph_bfs(graph, v[0])
|
|
print("\nBreadth-first traversal (BFS) vertex sequence is")
|
|
print(vets_to_vals(res))
|