add code for topological sort

Author: msdeep14

Diff for: README.md

@@ -1,3 +1,3 @@
-# geeksforgeeks practice
+# Algorithms practice
 
-My solutions to problem of [geeksforgeeks](http://www.geeksforgeeks.org/) portal
+This repository contains solutions to popular interview questions.

Diff for: a.out

@@ -0,0 +1,39 @@
+// https://www.geeksforgeeks.org/topological-sorting/
+#include <bits/stdc++.h>
+using namespace std;
+
+void topoSort(vector<vector<int> > &g, vector<int> &visited, int v, stack<int> &s){
+	visited[v] = 1;
+	for(int i=0;i<g[v].size();i++){
+		if(!visited[g[v][i]])
+			topoSort(g,visited,g[v][i],s);
+	}
+	s.push(v);
+}
+
+int main(){
+	vector<vector <int> > g;
+	int V = 6;
+	vector<int > visited;
+	g.resize(V+1);
+	visited.resize(V+1);
+	for(int i=0;i<V;i++)
+		visited[i] = 0;
+	g[5].push_back(0);
+	g[5].push_back(2);
+	g[4].push_back(0);
+	g[4].push_back(1);
+	g[2].push_back(3);
+	g[3].push_back(1);
+	stack<int > s;
+	for(int i=0;i<V;i++){
+		if(!visited[i])
+			topoSort(g,visited,i,s);
+	}
+	while(!s.empty()){
+		cout << s.top() << " ";
+		s.pop();
+	}
+	cout << endl;
+	return 0;
+}