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Data Structure

Graph Implementation as Adjacency List

import java.util.*;

class Graph_as_adjacencyList {
	private int V; // Number of vertices
	private ArrayList[] adj;
	Graph_as_adjacencyList(int v)
	{
		V = v;
        adj = new ArrayList[v];
		for (int i = 0; i < v; ++i)
		    adj[i] = new ArrayList();
	}
	void addEdge(int v, int w)
	{
		adj[v].add(w); //Creating an edge.
	}
    void showGraph(){
        for(int i=0;i"+adj[i].get(j));
            }
    }
}
class Graph_as_adjacencyList_Demo{
    public static void main(String[] args){
        Graph_as_adjacencyList g = new Graph_as_adjacencyList(4);
        g.addEdge(0, 1);
        g.addEdge(0, 2);
        g.addEdge(0, 3);
        g.addEdge(1, 2);
        g.addEdge(2, 0);
        g.addEdge(2, 3);
        g.addEdge(3, 3);
        g.addEdge(3, 1);
        g.showGraph();
    }
}