dfs.cs

/*
             *               1
             *             / | \
             *            2  5  9
             *           /  / \   \
             *          3  6   8   10
             *         /  / 
             *        4  7
             *
             */

            Graph graph = new Graph(11);
            graph.AddEdge(1, 2, false);
            graph.AddEdge(2, 3, false);
            graph.AddEdge(3, 4, false);
            graph.AddEdge(1, 5, false);
            graph.AddEdge(5, 6, false);
            graph.AddEdge(6, 7, false);
            graph.AddEdge(5, 8, false);
            graph.AddEdge(1, 9, false);
            graph.AddEdge(9, 10, false);
            graph.DFS();

    public class Graph
    {       
        LinkedList<int>[] linkedListArray;

        public Graph(int v)
        {
            linkedListArray = new LinkedList<int>[v];
        }

        /// 

        /// The method takes two nodes for which to add edge.
        /// 

        /// 
        /// 
        /// 
        public void AddEdge(int u, int v, bool blnBiDir = true)
        {
            if (linkedListArray[u] == null)
            {
                linkedListArray[u] = new LinkedList<int>();
                linkedListArray[u].AddFirst(v);
            }
            else
            {
                var last = linkedListArray[u].Last;
                linkedListArray[u].AddAfter(last, v);
            }

            if (blnBiDir)
            {
                if (linkedListArray[v] == null)
                {
                    linkedListArray[v] = new LinkedList<int>();
                    linkedListArray[v].AddFirst(u);
                }
                else
                {
                    var last = linkedListArray[v].Last;
                    linkedListArray[v].AddAfter(last, u);
                }
            }
        }

        internal void DFSHelper(int src, bool[] visited)
        {
            visited[src] = true;
            Console.Write(src + "->");
            if (linkedListArray[src] != null)
            {
                foreach (var item in linkedListArray[src])
                {
                    if (!visited[item] == true)
                    {
                        DFSHelper(item, visited);
                    }
                }
            }
        }

        internal void DFS()
        {
            Console.WriteLine("DFS");
            bool[] visited = new bool[linkedListArray.Length + 1];
            DFSHelper(1, visited);

        }
     }