加权无向图----加权无向图的实现

public class Edge implements Comparable<Edge> {    //实现Comparable接口
    private int v;
    private int w;
    private double weight;
	
    public Edge(int v,int w,double weight)
    { this.v = v; this.w = w; this.weight = weight;}

	//获取边的一个结点和另一个节点
    public int either() {return v;}
    public int other(int vertex) {
        if(vertex == v) return w;
        else if(vertex == w) return v;
    }
    //实现接口中的compareTo()方法
    public int compareTo(Edge that) {
        if(this.weight() < that.weight()) return -1;
        else if(this.weight() > that.weight()) return 1;
        else return 0;
    }

    public double weight() {return weight;}
    public String toString() { return String.format("%d-%d %.2f", v,w,weight); }
}

public class EdgeWeightedGraph {
    private int V;//顶点数
    private int E;//边数
    private Bag<Edge>[] adj;//一个边类型的背包

    public EdgeWeightedGraph(int V){
        this.V = V;
        this.E = 0;
        adj = (Bag<Edge>[]) new Bag[V];
        for(int v = 0; v < V; v++){
            adj[v] = new Bag<Edge>();    //二维数组
    }
	
    public int V() {return V;}
    public int E() {return E;}
	//添加边
    public void addEdge(Edge e) {
        //获取边的两个顶点
        int v = e.either();
        int w = e.other(v);
        //因为是无向图，互相添加边，调用的是背包的add()方法
        adj[v].add(e);   
        adj[w].add(e);
        E++;
    }
	//和v相关联的所有边
    public Iterable<Edge> adj(int v){ return adj[v]; }
    //图的所有边
    public Iterable<Edge> edges(){
        Bag<Edge> b = new Bag<Edge>();
        for(int v = 0; v <V ; v++)
            for(Edge e : adj[v])
                if(e.other(v)>v) b.add(e);
        return b;
    }
}