From 3b12578aa5d4c977a0cda943d4e86d0a1a8fc367 Mon Sep 17 00:00:00 2001
From: dadobt <danailvilos@gmail.com>
Date: Sun, 22 Oct 2017 21:18:53 +0200
Subject: [PATCH]  Topological Sort in Java

---
 Sorts/TopologicalSort.java | 83 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)
 create mode 100644 Sorts/TopologicalSort.java

diff --git a/Sorts/TopologicalSort.java b/Sorts/TopologicalSort.java
new file mode 100644
index 000000000000..851b7740aa79
--- /dev/null
+++ b/Sorts/TopologicalSort.java
@@ -0,0 +1,83 @@
+import java.io.*;
+import java.util.*;
+
+// This class represents a directed graph using adjacency
+// list representation
+class Graph
+{
+	private int V; // No. of vertices
+	private LinkedList<Integer> adj[]; // Adjacency List
+
+	//Constructor
+	Graph(int v)
+	{
+		V = v;
+		adj = new LinkedList[v];
+		for (int i=0; i<v; ++i)
+			adj[i] = new LinkedList();
+	}
+
+	// Function to add an edge into the graph
+	void addEdge(int v,int w) { adj[v].add(w); }
+
+	// A recursive function used by topologicalSort
+	void topologicalSortUtil(int v, boolean visited[],
+							Stack stack)
+	{
+		// Mark the current node as visited.
+		visited[v] = true;
+		Integer i;
+
+		// Recur for all the vertices adjacent to this
+		Iterator<Integer> it = adj[v].iterator();
+		while (it.hasNext())
+		{
+			i = it.next();
+			if (!visited[i])
+				topologicalSortUtil(i, visited, stack);
+		}
+
+		// Push current vertex to stack which stores result
+		stack.push(new Integer(v));
+	}
+
+	// The function to do Topological Sort. It uses
+	// recursive topologicalSortUtil()
+	void topologicalSort()
+	{
+		Stack stack = new Stack();
+
+		// Mark all the vertices as not visited
+		boolean visited[] = new boolean[V];
+		for (int i = 0; i < V; i++)
+			visited[i] = false;
+
+		// Call the recursive helper function to store
+		// Topological Sort starting from all vertices
+		// one by one
+		for (int i = 0; i < V; i++)
+			if (visited[i] == false)
+				topologicalSortUtil(i, visited, stack);
+
+		// Print contents of stack
+		while (stack.empty()==false)
+			System.out.print(stack.pop() + " ");
+	}
+
+	// Driver method
+	public static void main(String args[])
+	{
+		// Create a graph given in the above diagram
+		Graph g = new Graph(6);
+		g.addEdge(5, 2);
+		g.addEdge(5, 0);
+		g.addEdge(4, 0);
+		g.addEdge(4, 1);
+		g.addEdge(2, 3);
+		g.addEdge(3, 1);
+
+		System.out.println("Following is a Topological " +
+						"sort of the given graph");
+		g.topologicalSort();
+	}
+}
\ No newline at end of file