added DFS.cpp

Data Structures/DFS.cpp

@@ -0,0 +1,56 @@
+#include<bits/stdc++.h>
+using namespace std;
+#define MAXSIZE 1000000
+
+vector<vector<int> > graph(MAXSIZE);
+bool vis[MAXSIZE];
+
+
+void dfs(int start)
+{
+	stack<int> s;
+	cout<<start<<" ";
+	vis[start]=true;
+	s.push(start);
+	while(!s.empty())
+	{
+		int first=s.top();
+		for(int i=0;i<graph[first].size();i++)
+		{
+			if(!vis[graph[first][i]])
+			{
+				cout<<graph[first][i]<<" ";
+				vis[graph[first][i]]=true;
+				s.push(graph[first][i]);
+				first=graph[first][i];
+				i=-1;
+			}
+		}
+		s.pop();
+	}
+}
+int main()
+{
+
+	int n,u,v;
+	cin>>n;
+	for(int i=0;i<n-1;i++)
+	{
+		cin>>u>>v;
+		graph[u].push_back(v);
+		graph[v].push_back(u);
+	}
+
+	//to check adjacency list
+	// for(int i=1;i<=n;i++)
+	// {
+	// 	cout<<i<<"-> ";
+	// 	for(int j=0;j<graph[i].size();j++)
+	// 		cout<<graph[i][j]<<" ";
+	// 	cout<<endl;
+	// }
+
+	//dfs code
+	dfs(1);
+	return 0;
+}