NYOJ_1274_信道安全 -

别琢磨中间过程，我也整不清楚，死记住模板吧

     #include <stdio.h>
        #include <string.h>
        #include <queue>
        using namespace std;
        const int INF = 0x3f3f3f3f;
        const int Max_N = ;
        struct Node
        {
            int v;
            double w;
            int next;
        }edge[Max_N*];

        int head[Max_N];
        bool vis[Max_N];
        double dis[Max_N];
        int n,m,num;

        void add_edge(int u,int v,double w)
        {
            edge[num].v = v;
            edge[num].w = w;
            edge[num].next = head[u];
            head[u] = num++;
        }

        void SPFA()
        {
            int u,i,v;
            queue<int>Q;
            for(i=;i<=n;i++)
            {
                dis[i] = - INF;
            }
            memset(vis,false,sizeof(vis));
            dis[] = 1.0;
            vis[] = true;
            Q.push();
            while(!Q.empty())
            {
                u = Q.front();
                Q.pop();
                vis[u] = false;
                for(i=head[u];i!=-;i=edge[i].next)
                {
                    v = edge[i].v;
                    double w = edge[i].w;
                    if(dis[v]<dis[u]*w)
                    {
                        dis[v] = dis[u] * w;
                        if(!vis[v])
                        {
                            vis[v] = true;
                            Q.push(v);
                        }
                    }
                }
            }
        }
        int main()
        {
            int T;
            scanf("%d",&T);
            while(T--)
            {
                num = ;
                int i,j,a,b;
                double c;
                memset(head,-,sizeof(head));
                scanf("%d%d",&n,&m);
                for(i=;i<=m;i++)
                {
                    scanf("%d%d%lf",&a,&b,&c);
                    add_edge(a,b,c/);
                    add_edge(b,a,c/);
                }
                SPFA();
                printf("%lf\n",dis[n]*);
            }
            return ;
        }