Uva1025 A Spy in the Metro

#include <iostream>
#include <cstring>
#include <cstdio>

using namespace std;

int t[55];
int dp[55][222];                 //dp[i][j]记录在第i个车站需要等待时间
int l[55][222], r[55][222];      //l[i][j]第i个车站在j时刻是否有从左边行驶的车辆  r[i][j]右方向同l[i][j]
int num = 0;
int min(int a,int b){
    if(a<b) return a;
    return b;
}
int main()
{
    int n,T,m,cur;
    while (scanf("%d",&n)!=EOF )
    {
        memset(l, 0, sizeof(l));
        memset(r, 0, sizeof(r));
        memset(dp, 0x3f, sizeof(dp));
        cin>>T;
        for(int i=1;i<n;i++)    cin>>t[i];
        cin>>m;
        for(int i=1;i<=m;i++)
        {
            cin>>cur;
            for(int j=1;j<=n;j++)
            {
                l[j][cur] = 1, cur += t[j];
            }
        }
        cin>>m;
        for(int i=1;i<=m;i++)
        {
            cin>>cur;
            for(int j=n;j>0;j--)
            {
                r[j][cur] = 1, cur += t[j - 1];
            }
        }
        dp[n][T]=0;
        for(int j=T-1;j>=0;j--)
            for(int i=1;i<=n;i++)
            {
                dp[i][j]=dp[i][j+1]+1;
                if(l[i][j]) dp[i][j] = min(dp[i][j],dp[i+1][j+t[i]]);
                if(r[i][j]) dp[i][j] = min(dp[i][j],dp[i-1][j+t[i-1]]);
            }
        cout<< "Case Number "<<++num<<": ";
        if(dp[1][0]>T)
            cout<<"impossible"<<endl;
        else
            cout<<dp[1][0]<<endl;
    }
    return 0;
}