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TopologicalSort.java
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TopologicalSort.java
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package ds;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;
import java.util.Vector;
public class TopologicalSort {
int V;
List<Integer> adj[];
public TopologicalSort(int V)
{
this.V = V;
adj = new ArrayList[V];
for (int i = 0; i < V; i++)
adj[i] = new ArrayList<Integer>();
}
public void addEdge(int u, int v)
{
adj[u].add(v);
}
public void topologicalSort() {
int indegree[]=new int[V];
for(int i=0;i<V;i++) {
ArrayList<Integer> temp=(ArrayList<Integer>) adj[i];
for(int dest:temp) {
indegree[dest]++;
}
}
Queue<Integer> q=new LinkedList<Integer>();
for(int i=0;i<V;i++) {
if(indegree[i]==0)
q.add(i);
}
int order[]=new int[V];
int i=0;
while(!q.isEmpty()) {
int u=q.poll();
order[i++]=u;
for(int dest:adj[u]) {
indegree[dest]--;
if(indegree[dest]==0)
q.add(dest);
}
}
if(order.length!=V) {
System.out.println("There exists a cycle in the graph");
return;
}
for(int j:order) {
System.out.println(j);
}
}
public static void main(String args[])
{
TopologicalSort g = new TopologicalSort(9);
g.addEdge(0, 1);
g.addEdge(0, 4);
g.addEdge(1, 2);
g.addEdge(1, 6);
g.addEdge(3, 5);
g.addEdge(3, 4);
g.addEdge(3, 8);
g.addEdge(4, 8);
g.addEdge(4, 7);
g.addEdge(5, 6);
System.out.println("Topological Sort");
g.topologicalSort();
}
}