feature: Add csharp code graph_bfs and graph_dfs (#404)

* add csharp code graph_bfs and graph_dfs, modify graph adjacency list class inaccessable

* remove unnecessary using

* fix code style issue in comments

codes/csharp/chapter_graph/graph_adjacency_list.cs

@@ -10,10 +10,10 @@ using NUnit.Framework;
 namespace hello_algo.chapter_graph;
 
 /* 基于邻接表实现的无向图类 */
-class GraphAdjList
+public class GraphAdjList
 {
     // 邻接表，key: 顶点，value：该顶点的所有邻接顶点
-    Dictionary<Vertex, List<Vertex>> adjList;
+    public Dictionary<Vertex, List<Vertex>> adjList;
 
     /* 构造函数 */
     public GraphAdjList(Vertex[][] edges)

codes/csharp/chapter_graph/graph_bfs.cs

@@ -0,0 +1,68 @@
+/**
+ * File: graph_bfs.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_bfs
+    {
+        /* 广度优先遍历 BFS */
+        // 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 static List<Vertex> graphBFS(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>() { startVet };
+            // 队列用于实现 BFS
+            Queue<Vertex> que = new Queue<Vertex>();
+            que.Enqueue(startVet);
+            // 以顶点 vet 为起点，循环直至访问完所有顶点
+            while (que.Count > 0)
+            {
+                Vertex vet = que.Dequeue(); // 队首顶点出队
+                res.Add(vet);               // 记录访问顶点
+                foreach (Vertex adjVet in graph.adjList[vet])
+                {
+                    if (visited.Contains(adjVet))
+                    {
+                        continue;          // 跳过已被访问过的顶点
+                    }
+                    que.Enqueue(adjVet);   // 只入队未访问的顶点
+                    visited.Add(adjVet);   // 标记该顶点已被访问
+                }
+            }
+
+            // 返回顶点遍历序列
+            return res;
+        }
+
+        [Test]
+        public void Test()
+        {
+            /* 初始化无向图 */
+            Vertex[] v = Vertex.valsToVets(new int[10] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 });
+            Vertex[][] edges = new Vertex[12][]
+            {
+                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[1], v[4] }, new Vertex[2] { v[2], v[5] }, new Vertex[2] { v[3], v[4] },
+                new Vertex[2] { v[3], v[6] }, new Vertex[2] { v[4], v[5] }, new Vertex[2] { v[4], v[7] },
+                new Vertex[2] { v[5], v[8] }, new Vertex[2] { v[6], v[7] }, new Vertex[2] { v[7], v[8] }
+            };
+
+            GraphAdjList graph = new GraphAdjList(edges);
+            Console.WriteLine("\n初始化后，图为");
+            graph.print();
+
+            /* 广度优先遍历 BFS */
+            List<Vertex> res = graphBFS(graph, v[0]);
+            Console.WriteLine("\n广度优先遍历（BFS）顶点序列为");
+            Console.WriteLine(string.Join(" ", Vertex.vetsToVals(res)));
+        }
+    }
+}

codes/csharp/chapter_graph/graph_dfs.cs

@@ -0,0 +1,64 @@
+/**
+ * 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)));
+        }
+    }
+}