(简单) POJ 2502 Subway，Dijkstra。

#include <stdio.h>
#include <string.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <time.h>
    
using namespace std;

const int INF=10e8;

bool vis[300];

void Dijkstra(double lowcost[],double cost[][300],int N,int start)
{
    for(int i=1;i<=N;++i)
    {
        lowcost[i]=INF;
        vis[i]=0;
    }
    lowcost[start]=0;

    int k;
    double minn;

    for(int cas=1;cas<=N;++cas)
    {
        minn=INF;
        k=-1;

        for(int i=1;i<=N;++i)
            if(!vis[i] && minn>lowcost[i])
            {
                minn=lowcost[i];
                k=i;
            }

        if(k==-1)
            return;

        vis[k]=1;

        for(int i=1;i<=N;++i)
            if(!vis[i] && cost[k][i]>=0 && lowcost[i]>lowcost[k]+cost[k][i])
                lowcost[i]=lowcost[k]+cost[k][i];
    }
}

int X[300],Y[300];
int N;
double map1[300][300];
double ans[300];

double getdis(int a,int b)
{
    return sqrt((double(X[a]-X[b]))*(X[a]-X[b])+(double(Y[a]-Y[b]))*(Y[a]-Y[b]));
}

int main()
{
    //freopen("in.txt","r",stdin);
    //freopen("out.txt","w",stdout);

    for(int i=1;i<=250;++i)
        for(int j=1;j<=250;++j)
            map1[i][j]=-1;

    scanf("%d %d %d %d",&X[1],&Y[1],&X[2],&Y[2]);
    
    N=3;
    int base;

    while(~scanf("%d %d",&X[N],&Y[N]))
    {
        base=N;
        while(X[N]!=-1 || Y[N]!=-1)
        {
            ++N;
            scanf("%d %d",&X[N],&Y[N]);
        }

        for(int i=base;i<N-1;++i)
            map1[i][i+1]=map1[i+1][i]=3.0*getdis(i,i+1)/2000.0;
    }
    --N;

    for(int i=1;i<=N;++i)
        for(int j=1;j<=i;++j)
            if(map1[i][j]<0)
                map1[i][j]=map1[j][i]=3.0*getdis(i,j)/500.0;

    Dijkstra(ans,map1,N,1);

    printf("%d\n",(int)(ans[2]+0.5));
    
    return 0;
}