/**
 * File: graph_dfs.cs
 * Created Time: 2023-03-08
 * Author: hpstory (hpstory1024@163.com)
 */

using hello_algo.include;
using NUnit.Framework;

namespace hello_algo.chapter_graph
{
    public class graph_dfs
    {
        /* 深度优先遍历 DFS 辅助函数 */
        public void dfs(GraphAdjList graph, HashSet<Vertex> visited, List<Vertex> res, Vertex vet)
        {
            res.Add(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
            foreach (Vertex adjVet in graph.adjList[vet])
            {
                if (visited.Contains(adjVet))
                {
                    continue; // 跳过已被访问过的顶点                             
                }
                // 递归访问邻接顶点
                dfs(graph, visited, res, adjVet);
            }
        }

        /* 深度优先遍历 DFS */
        // 使用邻接表来表示图，以便获取指定顶点的所有邻接顶点
        public List<Vertex> graphDFS(GraphAdjList graph, Vertex startVet)
        {
            // 顶点遍历序列
            List<Vertex> res = new List<Vertex>();
            // 哈希表，用于记录已被访问过的顶点
            HashSet<Vertex> visited = new HashSet<Vertex>();
            dfs(graph, visited, res, startVet);
            return res;
        }

        [Test]
        public void Test()
        {
            /* 初始化无向图 */
            Vertex[] v = Vertex.valsToVets(new int[7] { 0, 1, 2, 3, 4, 5, 6 });
            Vertex[][] edges = new Vertex[6][]
            {
                new Vertex[2] { v[0], v[1] }, new Vertex[2] { v[0], v[3] }, new Vertex[2] { v[1], v[2] },
                new Vertex[2] { v[2], v[5] }, new Vertex[2] { v[4], v[5] }, new Vertex[2] { v[5], v[6] },
            };

            GraphAdjList graph = new GraphAdjList(edges);
            Console.WriteLine("\n初始化后，图为");
            graph.print();

            /* 深度优先遍历 DFS */
            List<Vertex> res = graphDFS(graph, v[0]);
            Console.WriteLine("\n深度优先遍历（DFS）顶点序列为");
            Console.WriteLine(string.Join(" ", Vertex.vetsToVals(res)));
        }
    }
}