Example-09-01

#define _CRT_SECURE_NO_WARNINGS

#include <cstdio>
#include <cstring>

int min(int a, int b)
{
if (a < b) return a;
else return b;
}

int main()
{
int N; // 2 <= N <= 50
int t[55];
int T; // 0 <= T <= 200
int M1, M2; // 1 <= M1, M2 <= 50
int d[55], e[55];

int have_train[205][55][2]; // [time][station][direction]
// time <= 200
// sation <= 50
// direction == 0 left, == 1 right

int kase = 1;

while (scanf("%d", &N) && N) {
scanf("%d", &T);
for (int i = 1; i < N; i++)
scanf("%d", &t[i]); // t[i] is the time between station i and station i+1

memset(have_train, 0, sizeof(have_train));

scanf("%d", &M1);

for (int i = 0; i < M1; i++){ // for each train
int start;
scanf("%d", &start);
have_train[start][1][0] = 1; // station 1
for (int j = 1; j < N; j++) { // station 2, 3, 4..., N; j+1 is the station number
// start + t[j] is the time the train arrives at station j+1, also is start time + time from station 1 to station j+1
// t[j] is the time between station j and station j+1
if (start + t[j] <= T) {
have_train[start + t[j]][j + 1][0] = 1;
}
start += t[j];
}
}

scanf("%d", &M2);
for (int i = 0; i < M2; i++){ // for each train
int start;
scanf("%d", &start);
have_train[start]
[1] = 1; // station N
for (int j = N-1; j >= 1; j--) { // station N-1, N-2, ..., 1; j is the station number
// start + t[j] is the time the train arrives at station j, also is start time + time from station N to station j
// t[j] is the time between station j and station j+1
if (start + t[j] <= T) {
have_train[start + t[j]][j][1] = 1;
}
start += t[j];
}
}

#define INF 10000000
int counts = 0;
int dp[205][205];

for (int i = 1; i <= N-1; i++)
dp[T][i] = INF;
dp[T]
 = 0;

for (int i = T - 1; i >= 0; i--){
for (int j = 1; j <= N; j++){
dp[i][j] = dp[i+1][j] + 1;
if (j < N && i + t[j] <= T && have_train[i][j][0]){
dp[i][j] = min(dp[i][j], dp[i+t[j]][j+1]); // t[j] is the time between station j and station j+1
}
if (j > 1 && i + t[j-1] <= T && have_train[i][j][1]){
dp[i][j] = min(dp[i][j], dp[i+t[j-1]][j-1]); // t[j-1] is the time between station j-1 and station j
}
}
}

if (dp[0][1] >= INF)
printf("Case Number %d: impossible\n", ++counts);
else
printf("Case Number %d: %d\n", ++counts, dp[0][1]);

}

return 0;
}