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hello-algo/codes/python/chapter_graph/graph_dfs.py

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"""
File: graph_dfs.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, vets_to_vals, vals_to_vets
from graph_adjacency_list import GraphAdjList
def dfs(graph: GraphAdjList, visited: set[Vertex], res: list[Vertex], vet: Vertex):
"""深度优先遍历辅助函数"""
res.append(vet) # 记录访问顶点
visited.add(vet) # 标记该顶点已被访问
# 遍历该顶点的所有邻接顶点
for adjVet in graph.adj_list[vet]:
if adjVet in visited:
continue # 跳过已被访问的顶点
# 递归访问邻接顶点
dfs(graph, visited, res, adjVet)
def graph_dfs(graph: GraphAdjList, start_vet: Vertex) -> list[Vertex]:
"""深度优先遍历"""
# 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 = []
# 哈希表,用于记录已被访问过的顶点
visited = set[Vertex]()
dfs(graph, visited, res, start_vet)
return res
"""Driver Code"""
if __name__ == "__main__":
# 初始化无向图
v = vals_to_vets([0, 1, 2, 3, 4, 5, 6])
edges = [
[v[0], v[1]],
[v[0], v[3]],
[v[1], v[2]],
[v[2], v[5]],
[v[4], v[5]],
[v[5], v[6]],
]
graph = GraphAdjList(edges)
print("\n初始化后,图为")
graph.print()
# 深度优先遍历
res = graph_dfs(graph, v[0])
print("\n深度优先遍历DFS顶点序列为")
print(vets_to_vals(res))