UVa 1025 A Spy in the Metro

 1 /**/
 2 #include<iostream>
 3 #include<cstdio>
 4 #include<cmath>
 5 #include<cstring>
 6 #include<algorithm>
 7 using namespace std;
 8 const int mxn=300;
 9 int n,T;
10 bool h[mxn][mxn][2];
11 int ti[mxn];
12 int m,d,e;
13 int f[mxn][mxn];
14 void clear(){
15     memset(ti,0,sizeof(ti));
16     memset(h,0,sizeof(h));
17     memset(f,111,sizeof(f));
18 }
19 int main(){
20     int cnt=0;
21     while(scanf("%d",&n) && n){
22         clear();
23         scanf("%d",&T);
24         int i,j;
25         for(i=1;i<n;i++)scanf("%d",&ti[i]);//车站距离 
26         scanf("%d",&m);
27         for(i=1;i<=m;i++)
28         {
29             scanf("%d",&d);//左边发车时间 
30             for(j=1;d<=T && j<=n;d+=ti[j],j++){
31                 h[d][j][0]=1;
32             }
33         }
34         scanf("%d",&m);
35         for(i=1;i<=m;i++)
36         {
37             scanf("%d",&e);//右边发车时间
38             for(j=n;e<=T && j>=1;j--,e+=ti[j]){
39                 h[e][j][1]=1;
40             }
41         }
42         //以上全是初始化 
43         f[T][n]=0;
44         for(i=T-1;i>=0;i--){//倒推 
45             for(j=1;j<=n;j++){
46                 f[i][j]=f[i+1][j]+1;//等待
47                 if(j<n && h[i][j][0] && i+ti[j]<=T)
48                     f[i][j]=min(f[i][j],f[i+ti[j]][j+1]);//向右
49                 if(j>1 && h[i][j][1] && i+ti[j-1]<=T)
50                     f[i][j]=min(f[i][j],f[i+ti[j-1]][j-1]);//向左 
51             }
52         }
53         printf("Case Number %d: ",++cnt);
54         if(f[0][1]>=0xff) printf("impossible\n");
55         else printf("%d\n",f[0][1]);
56     }
57     return 0;
58 }