_155topoSort.java

import java.util.*;
public class _155topoSort {
    static class Edge{
        int src;
        int dest;
        public Edge(int s, int d){
            this.src=s;
            this.dest=d;
        }
    }
    static void createGraph(ArrayList<Edge>[] graph){
        for(int i=0;i<graph.length;i++){
            graph[i]=new ArrayList<>();
        }
        graph[2].add(new Edge(2,3));

        graph[3].add(new Edge(3,1));

        graph[4].add(new Edge(4,0));
        graph[4].add(new Edge(4,1));
        
        graph[5].add(new Edge(5,0));
        graph[5].add(new Edge(5,2));
    }
    public static void topSort(ArrayList<Edge>[] graph){
        boolean vis[]=new boolean[graph.length];
        Stack<Integer> s =new Stack<>();
        for(int i = 0; i<graph.length;i++){
            if(!vis[i]){
                topSortUtil(graph,i,vis,s);
            }
        }
        while(!s.isEmpty()){
            System.out.print(s.pop()+" ");
        }
    }
    public static void topSortUtil(ArrayList<Edge>[] graph, int curr,boolean vis[],Stack<Integer> s){
        vis[curr]=true;
        for(int i = 0; i<graph[curr].size();i++){
            Edge e = graph[curr].get(i);
            if(!vis[e.dest]){
                topSortUtil(graph, e.dest, vis, s);
            }
        }
        s.push(curr);
    }
    public static void main(String[] args) {
        int V = 6;
        @SuppressWarnings("unchecked")
        ArrayList<Edge> graph[] = new ArrayList[V];
        createGraph(graph);
        topSort(graph);
    }
}