【动态规划】[UVA1025]A Spy in the Metro 城市里的间谍

参考：https://blog.csdn.net/NOIAu/article/details/71517440

https://blog.csdn.net/c20180630/article/details/75245665

https://blog.csdn.net/rechard_chen/article/details/41357173

https://blog.csdn.net/acvay/article/details/43565183

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
const int N=55;
const int M=210;
const int INF=1e8;
int n,t,l,r,kcase;//n车站数，t时间，l向右车辆数，kcase样例数
int station_time[N];//车站之间的时间
int have_train[M][N][3],dp[M][N];
void test()
{
    cout<<'n'<<n<<'t'<<t<<endl;
    for (int i=0;i<n;i++)
    {
        cout<<station_time[i]<<' ';
    }
    cout<<endl;
    for (int i=0;i<=t;i++)
    {
        for (int j=0;j<=n;j++)
        {
            printf("[%9d]",dp[i][j]);
        }
        printf("
");
    }
    getchar();
}
void init()
{
    cin>>t;
    memset(station_time,0,sizeof(station_time));
    for (int i=0;i<n-1;i++)
    {
        cin>>station_time[i];
    }
    cin>>r;
    memset(have_train,0,sizeof(have_train));
    while (r--)
    {
        int d;
        cin>>d;
        for (int j=1;j<n;j++)
        {
            if (d<=t)
            {
                have_train[d][j][0]=1;
            }
            d+=station_time[j-1];
        }
    }
    cin>>l;
    while (l--)
    {
        int d;
        cin>>d;
        for (int j=n;j>1;j--)
        {
            if (d<=t)
            {
                have_train[d][j][1]=1;
            }
            d+=station_time[j-2];
        }
    }
}
void dpp()
{
    memset(dp,0,sizeof(dp));
    for (int j=1;j<=n;j++)
    {
        dp[t][j]=INF;
    }
    dp[t][n]=0;
    for (int i=t-1;i>=0;i--)//注意i>=0!
    {
        for (int j=1;j<=n;j++)
        {
            dp[i][j]=dp[i+1][j]+1;
            if (j<n&&have_train[i][j][0]&&i+station_time[j-1]<=t)
            {
                dp[i][j]=min(dp[i][j],dp[i+station_time[j-1]][j+1]);
            }
            if (j>1&&have_train[i][j][1]&&i+station_time[j-2]<=t)//注意判断条件不要写错！
            {
                dp[i][j]=min(dp[i][j],dp[i+station_time[j-2]][j-1]);
            }
        }

    }
//    test();
    cout<<"Case Number "<<kcase++<<": ";
    if (dp[0][1]>=INF)
    {
        cout<<"impossible"<<endl;
    }
    else
    {
        cout<<dp[0][1]<<endl;
    }
}
int main()
{
    kcase=1;
//    freopen("btext.txt","r",stdin);
    while (cin>>n&&n)
    {
        init();
        dpp();
    }

    return 0;
}