public class Node {
    public int value;
    public int in;
    public int out;
    public ArrayList<Node> nexts;
    public ArrayList<Edge> edges;

    public Node(int value) {
        this.value = value;
        in = 0;
        out = 0;
        nexts = new ArrayList<>();
        edges = new ArrayList<>();
    }
}

public class Edge {
    Node from;
    Node to;
    int weight;

    public Edge(Node from, Node to, int weight) {
        this.from = from;
        this.to = to;
        this.weight = weight;
    }
}

public class Graph {
    public HashMap<Integer, Node> nodes;
    public Set<Edge> edges;

    public Graph() {
        nodes = new HashMap<>();
        edges = new HashSet<>();
    }
}

public static Graph createGraph(int[][] matrix) {
        // 初始化一個圖
        Graph graph = new Graph();

        for (int[] arr : matrix) {
            // 來的點
            int from = arr[0];
            // 去的點
            int to = arr[1];
            // 權重
            int value = arr[2];

            // 生成相對應的點
            Node fromNode = new Node(from);
            Node toNode = new Node(to);

            // 查看當前有沒有這個點的信息
            if (!graph.nodes.containsKey(from)) {
                graph.nodes.put(from, fromNode);
            }
            if (!graph.nodes.containsKey(to)) {
                graph.nodes.put(to, toNode);
            }

            // 生成一個邊(這里的邊是有向邊)
            Edge edge = new Edge(fromNode, toNode, value);

            // 點里面加入邊
            graph.nodes.get(from).edges.add(edge);

            //  點里面加入下一個點
            graph.nodes.get(from).nexts.add(toNode);

            // 點里面加入入度和出度
            graph.nodes.get(from).out++;
            graph.nodes.get(to).in++;

            // 圖里面加入邊
            graph.edges.add(edge);

        }
        return graph;
    }

public static void main(String[] args) {
        int[][] arr = new int[][]{{2, 1, 1}, {2, 3, 1}, {3, 4, 1}};
        Graph graph = createGraph(arr);
        // 從2開始的邊有哪些
        List<Edge> edgeList = graph.nodes.get(2).edges;
        for (Edge edge : edgeList) {
            System.out.println("從" + edge.from.value + "---->" + edge.to.value + "權值為" + edge.weight);
        }
    }