如何在图中找到特定顶点的度数？

Question

    import java.util.*;
    import java.io.*;
    public class homework{
        static class Graph {
            private LinkedList<Integer> adjLists[];
            private boolean visited[];
            private int V;

            // Graph creation
            Graph(int vertices) {
                V = vertices;
                adjLists = new LinkedList[vertices];
                visited = new boolean[vertices];

                for (int i = 0; i < vertices; i++)
                    adjLists[i] = new LinkedList();
            }

            // Add edges to the graph
            void addEdge(int vertices, int dest) {
                adjLists[vertices].add(dest);
            }

            // DFS algorithm
            void DFS(int vertex) {
                visited[vertex] = true;
                System.out.print(vertex + " ");

                Iterator<Integer> ite = adjLists[vertex].listIterator();
                while (ite.hasNext()) {
                    int adj = ite.next();
                    if (!visited[adj])
                        DFS(adj);
                }
            }
            //BFS algorithm
            void BFS(int s) {
                boolean visited[] = new boolean[V];
                visited[s] = true;
                LinkedList<Integer> queue = new LinkedList<>();
                queue.add(s);
                while (queue.size() != 0) {
                    s = queue.poll();
                    System.out.println(s + " ");

                    Iterator<Integer> i = adjLists[s].listIterator();
                    while (i.hasNext()) {
                        int n = i.next();
                        if (!visited[n]) {
                            visited[n] = true;
                            queue.add(n);
                        }
                    }
                }
            }

            public static void main(String args[]) {
                Graph g = new Graph(4);

                g.addEdge(0, 1);
                g.addEdge(0, 2);
                g.addEdge(1, 2);
                g.addEdge(2, 0);
                g.addEdge(2, 3);
                g.addEdge(3, 3);

                System.out.println("Following is Depth First Traversal");

                g.DFS(2);

                System.out.println("Flowing is BFS");
                g.BFS(2);

                int degree = findDegree(G, dest);
                System.out.println(degree);
            }
        }
    }

I apologize if I made too many mistakes, but I don't have much experience with java.I have been trying to create a method that find the degree of the vertex .My other methods work like a charm at least for a beginner like me.

static int findDegree(Graph G,int dest){
            int degree = 0;
            for(int i = 0; i < G.dest;i++){
                if(G.dest[i] == 1){
                    degree++;
                }
                return degree;
            }
        }

I tried like this but getting errors that saying (G cannot be resolved to a variable,dest cannot be resolved to a variable).Is there a way to solve this or should i just change the findDegree() method.

Answer 1

This is such a simple and silly mistake, but it happens with everyone.

I think the problem is with the line:

int degree = findDegree(G, dest);

Firstly, change the variable 'G' to 'g' as you have declared small 'g' in your code above. Secondly, either initialise dest:

int dest = 3;

or just pass a number:

int degree = findDegree(g, 3);

Hope it helps.

Answer 2

Make an array deg[n] where n is the number of vertices in the graph and whenever you take an edge input x and y, if the graph is undirected then increment deg[x] and deg[y]. If the graph is directed then only do deg[x]++.