From 94e9f5771aa58883e216154e9dd3f24e2de4c4a4 Mon Sep 17 00:00:00 2001
From: Amulya Gaur <amulyagaur111@gmail.com>
Date: Sun, 28 Oct 2018 18:52:48 +0530
Subject: [PATCH] added Topological Sorting code in c++

C++ code to find lexicographically smallest topological order of a DAG.
---
 OPEN CHALLENGE/TopoSort.cpp | 43 +++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 OPEN CHALLENGE/TopoSort.cpp

diff --git a/OPEN CHALLENGE/TopoSort.cpp b/OPEN CHALLENGE/TopoSort.cpp
new file mode 100644
index 00000000..84939355
--- /dev/null
+++ b/OPEN CHALLENGE/TopoSort.cpp	
@@ -0,0 +1,43 @@
+//Prints the Lexicographically smallest TS order.
+#include <bits/stdc++.h>
+using namespace std;
+#define endl '\n'
+vector< vector<int> > v(100);
+vector<bool> visit(100,false);
+stack<int> st;
+void toposort(int s)
+{
+	visit[s]=true;
+	for(int i=0;i<v[s].size();i++)
+	{
+		if(visit[v[s][i]]==false)
+		{
+			toposort(v[s][i]);
+		}
+	}
+	st.push(s);
+}
+int main()
+{
+    ios_base::sync_with_stdio(false);
+    cin.tie(NULL);
+    int n,m;
+    cin>>n>>m;
+    while(m--)
+    {
+    	int x,y;
+    	cin>>x>>y;
+    	v[x].push_back(y);
+    }
+    for(int i=1;i<=n;i++)
+    sort(v[i].rbegin(),v[i].rend());
+    for(int i=n;i>=1;i--)
+    if(visit[i]==false)
+    toposort(i);
+    while(!st.empty())
+    {
+        cout<<st.top()<<" ";
+        st.pop();
+    }
+    return 0;
+}