Lab7q4.java

import java.util.ArrayList;

public class Lab7q4 {
    public static void main(String[] args) {
        
        ArrayList<ArrayList<Integer>> list= new ArrayList<>();
        int vertices=4;

        for(int i=0;i<vertices;i++){
            list.add(new ArrayList<>());
        }

        list.get(0).add(1);
        list.get(0).add(2);
        list.get(1).add(3);
        list.get(2).add(1);
        list.get(3).add(2);

        System.out.println("Adjancecy list is:");
        for(int j=0;j<list.size();j++){
            System.out.print(j+ " : { ");
            for(Integer element: list.get(j)){
                System.out.print(element + " ");
            }
            System.out.println(" }");
        }

        int[][] matrix= new int[vertices][vertices];

        matrix=convertListToMatrix(list);

        System.out.println("Adjancecy matrix is:");
        for(int i=0;i<list.size();i++){
            for(int j=0;j<list.size();j++){
                System.out.print(matrix[i][j]+ " ");
            }
            System.out.println("");
        }

    }

    private static int[][] convertListToMatrix(ArrayList<ArrayList<Integer>> list){
        int vertices= list.size();
        int[][] matrix = new int[vertices][vertices];

        for(int i=0;i<vertices;i++){
            for(Integer element : list.get(i)){
                matrix[i][element]=1;
                //matrix[element][i]=1;
            }
        }

        return matrix;
    }
}