HDU - 2680-Choose the best route 最短路径模板题

不念不忘少年蓝@ 2022-06-06 00:58 157阅读 0赞

# Choose the best route #

One day , Kiki wants to visit one of her friends. As she is liable to carsickness , she wants to arrive at her friend’s home as soon as possible . Now give you a map of the city’s traffic route, and the stations which are near Kiki’s home so that she can take. You may suppose Kiki can change the bus at any station. Please find out the least time Kiki needs to spend. To make it easy, if the city have n bus stations ,the stations will been expressed as an integer 1,2,3…n.

## Input ##

There are several test cases.  
Each case begins with three integers n, m and s,(n<1000,m<20000,1=<s<=n) n stands for the number of bus stations in this city and m stands for the number of directed ways between bus stations .(Maybe there are several ways between two bus stations .) s stands for the bus station that near Kiki’s friend’s home.  
Then follow m lines ,each line contains three integers p , q , t (0<t<=1000). means from station p to station q there is a way and it will costs t minutes .  
Then a line with an integer w(0<w<n), means the number of stations Kiki can take at the beginning. Then follows w integers stands for these stations.

## Output ##

The output contains one line for each data set : the least time Kiki needs to spend ,if it’s impossible to find such a route ,just output “-1”.

## Sample Input ##

5 8 5
    1 2 2
    1 5 3
    1 3 4
    2 4 7
    2 5 6
    2 3 5
    3 5 1
    4 5 1
    2
    2 3
    4 3 4
    1 2 3
    1 3 4
    2 3 2
    1
    1

## Sample Output ##

1
    -1

#include <bits/stdc++.h>//Choose the best route
    using namespace std;
    #define INF 0x3f3f3f3f
    int Tu[1002][1002];//存储图的信息
    int dis[1002];//到源点的最短距离
    int bj[1002];//标记这个点有没有访问过
    int N,M,S;
    void init()//数据的初始化
    {
        for(int i=0; i<=N; i++)
            for(int j=0; j<=N; j++)
            {
                if(i==j)
                    Tu[i][j]=0;
                else
                    Tu[i][j]=INF;
            }
    }
    void dij()
    {
        for(int i=0; i<=N; i++)
        {
            dis[i]=Tu[0][i];//源点到i点的最短距离
            bj[i]=0;//标记这个点有没有访问过
        }
        bj[0]=1;
        int flag=0;//下一个起始点
        int c=1;//保存点的个位数
        while(c<N)
        {
            int Min=INF;
            for(int i=0; i<=N; i++)
            {
                if(bj[i]==0&&dis[i]<Min)//找到下一个最短距离
                {
                    Min=dis[i];
                    flag=i;
                }
            }
            bj[flag]=1;//标记flag点访问过
            c++;//城市个数加
            for(int i=0;i<=N;i++)
                if(bj[i]==0&&dis[i]>dis[flag]+Tu[flag][i])//这个点没有访问过并且最短距离可以更新
                {
                    dis[i]=dis[flag]+Tu[flag][i];
                }
        }
    }
    int main()
    {
        int p,q,t,a,w;
        while(scanf("%d%d%d",&N,&M,&S)!=EOF)
        {
            init();
            while(M--)
            {
                scanf("%d%d%d",&p,&q,&t);
                Tu[p][q]=min(Tu[p][q],t);
            }
            scanf("%d",&w);
            while(w--)
            {
                scanf("%d",&a);
                Tu[0][a]=Tu[a][0]=0;
            }
            dij();
            if(dis[S]!=INF)
            printf("%d\n",dis[S]);
            else
                printf("-1\n");
        }
        return 0;
    }