"""
File: graph_dfs.py
Created Time: 2023-02-23
Author: Krahets (krahets@163.com)
"""

import sys, os.path as osp
sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
from modules import *
from graph_adjacency_list import GraphAdjList

def dfs(graph: GraphAdjList, visited: Set[Vertex], res: List[Vertex], vet: Vertex):
    """ 深度优先遍历 DFS 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 # 跳过已被访问过的顶点
        # 递归访问邻接顶点
        dfs(graph, visited, res, adjVet)

# 使用邻接表来表示图，以便获取指定顶点的所有邻接顶点
def graph_dfs(graph: GraphAdjList, start_vet: Vertex) -> List[Vertex]:
    """ 深度优先遍历 DFS """
    # 顶点遍历序列
    res = []
    # 哈希表，用于记录已被访问过的顶点
    visited = set()
    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 DFS
    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))