added dfs code

dfs.cpp

@@ -0,0 +1,56 @@
+#include<iostream>
+#include<list>
+#include<vector>
+#define pb push_back
+using namespace std;
+
+class Graph{
+     public:
+     int V;
+     list<int> *adj;
+
+    Graph(int v){
+         V=v;
+         adj = new list<int>[V];
+    }
+     void addEdge(int u,int v,bool isUndirected=true){
+          adj[u].pb(v);
+          if(isUndirected==false){
+               adj[v].pb(u);
+          }
+     }
+    void dfsHelper(int node,vector<bool>&visited){
+         visited[node]=true;
+         cout<<node<<" ";
+         for(auto nbr:adj[node]){
+              if(!visited[nbr]){
+                   dfsHelper(nbr,visited);
+              }
+         }
+     return;
+    }
+     void dfs(int src){
+          vector<bool>visited(V,false);
+          dfsHelper(src,visited);
+     }
+
+
+
+
+};
+
+int main(){
+Graph g(7);
+g.addEdge(0, 1);
+    g.addEdge(0, 2);
+    g.addEdge(1, 2);
+    g.addEdge(2, 0);
+    g.addEdge(2, 3);
+    g.addEdge(3, 3);
+
+    cout << "Following is Depth First Traversal "
+         << "(starting from vertex 2) \n";
+    g.dfs(2);
+
+    return 0;
+}