Q42 Mother Vertex | Interviewbit (kosraju)

public class Solution {
    public int motherVertex(int v, ArrayList<ArrayList<Integer>> edges) {
        // Q42 graph playlist , based on kosraju
		
        //make graph 
        ArrayList<ArrayList<Integer>> graph = new ArrayList<>();
        
        for(int i = 0 ;i < v ; i++)
        graph.add(new ArrayList<>());
            
        
        
        for(ArrayList<Integer> edge : edges){
            int a = edge.get(0)-1  , b = edge.get(1)-1;

            graph.get(a).add(b);
        }
        
        //fire DFS and add nodes while backtracking
        boolean visited[] = new boolean[v];
        LinkedList<Integer> st = new LinkedList<>();
        
        for(int i = 0 ;i < v ; i++){
            
            if(visited[i] == false)
            dfs(graph , i , visited , st);
        }
        
        //now our potential answer is stored in the top of the stack
        visited = new boolean[v];
        count = 0;
        int potential = st.pop();
        
        //apply DFS and check in count if all nodes are getting visited
        dfs2(graph , potential , visited);
        
        //return count if all nodes got visited;
        return count == v ? 1 : 0;
    }
    
    static int count;
    public static void dfs(ArrayList<ArrayList<Integer>> graph , int source , boolean visited[] 
    , LinkedList<Integer> st){
        
        visited[source] = true;
        
        for(int nbr : graph.get(source)){
            if(visited[nbr] == false)
            dfs(graph , nbr , visited , st);
        }
        
        st.addFirst(source);
    }
    
    public static void dfs2(ArrayList<ArrayList<Integer>> graph , int source , boolean visited[]){
        
        visited[source] = true;
        count ++;
        for(int nbr : graph.get(source)){
            if(visited[nbr] == false)
            dfs2(graph , nbr , visited);
        }
    }

}