Graph-matrix

public class Node {
  int data;
  public Node(int data) {
    this.data = data;
   }
}

public class Graph {
  int size;
  ArrayList<Node> vertices;
  int[][] matrix;
  
  //Constructor
  public Graph(int size) {
    this.size = size;
    vertices = new ArrayList<>();
    matrix = new matrix[size][size];
  }
  
  //vertex 추가하기!
  public void addVertex(Node node) {
    vertices.add(node);
  }
  
  //edges 추가하기!
  public void addEdges(int from, int to) {
    matrix[from][to] = 1;
  }