AC代码：

#include <bits/stdc++.h>
using namespace std;
const int maxn = 255;
const int INF = 1e9;
int n, T, t[maxn], m1, d[maxn], m2, e[maxn];
int f[maxn][maxn];
bool tl[maxn][maxn], tr[maxn][maxn];

void init() {
	for (int i = 1; i <= n; i++)
		for (int j = 0; j <= T; j++)
			f[i][j] = INF, tl[i][j] = tr[i][j] = 0;
	f[1][0] = 0;
}

int main() {
	for (int cas = 1; ; cas++) {
		scanf("%d", &n);
		if (!n) break;
		scanf("%d", &T);
		for (int i = 1; i < n; i++)
			scanf("%d", t+i);
		scanf("%d", &m1);
		for (int i = 1; i <= m1; i++)
			scanf("%d", d+i);
		scanf("%d", &m2);
		for (int i = 1; i <= m2; i++)
			scanf("%d", e+i);
		init();
		for (int i = 1; i <= m1; i++) {
			int x = d[i];
			tr[1][x] = true;
			for (int j = 2; j <= n; j++) {
				x += t[j-1];
				if (x > T) break;
				tr[j][x] = true;	
			}
		}
		for (int i = 1; i <= m2; i++) {
			int x = e[i];
			tl[n][x] = true;
			for (int j = n-1; j >= 1; j--) {
				x += t[j];
				if (x > T) break;
				tl[j][x] = true;
			}
		}
		for (int j = 0; j < T; j++) {
			for (int i = 1; i <= n; i++) {
				if (f[i][j] == INF)
					continue;
				f[i][j+1] = min(f[i][j+1], f[i][j] + 1);
				if (i < n && tr[i][j]) {
					int y = j + t[i];
					if (y <= T)
						f[i+1][y] = min(f[i+1][y], f[i][j]);
				}
				if (i > 1 && tl[i][j]) {
					int y = j + t[i-1];
					if (y <= T)
						f[i-1][y] = min(f[i-1][y], f[i][j]);
				}
			}
				
		}
		if (f[n][T] == INF)
			printf("Case Number %d: impossible\n", cas);
		else
			printf("Case Number %d: %d\n", cas, f[n][T]);
	}
	return 0;
}

错误代码：

#include <bits/stdc++.h>
using namespace std;
const int maxn = 255;
const int INF = 1e9;
int n, T, t[maxn], m1, d[maxn], m2, e[maxn];
int f[maxn][maxn];
bool tl[maxn][maxn], tr[maxn][maxn];

void init() {
	for (int i = 1; i <= n; i++)
		for (int j = 0; j <= T; j++)
			f[i][j] = INF, tl[i][j] = tr[i][j] = 0;
	f[1][0] = 0;
}

int main() {
	for (int cas = 1; ; cas++) {
		scanf("%d", &n);
		if (!n) break;
		scanf("%d", &T);
		for (int i = 1; i < n; i++)
			scanf("%d", t+i);
		scanf("%d", &m1);
		for (int i = 1; i <= m1; i++)
			scanf("%d", d+i);
		scanf("%d", &m2);
		for (int i = 1; i <= m2; i++)
			scanf("%d", e+i);
		init();
		for (int i = 1; i <= m1; i++) {
			int x = d[i];
			tr[1][x] = true;
			for (int j = 2; j <= n; j++) {
				x += t[j-1];
				if (x > T) break;
				tr[j][x] = true;	
			}
		}
		for (int i = 1; i <= m2; i++) {
			int x = e[i];
			tl[n][x] = true;
			for (int j = n-1; j >= 1; j--) {
				x += t[j];
				if (x > T) break;
				tl[j][x] = true;
			}
		}
		for (int j = 0; j < T; j++) {
			for (int i = 1; i <= n; i++) {
				if (f[i][j] == INF)
					continue;
				f[i][j+1] = min(f[i][j+1], f[i][j] + 1);
				if (i < n && tr[i][j]) {
					int y = j + t[i];
					if (y <= T)
						f[i+1][y] = min(f[i+1][y], f[i][j]);
				}
				if (i > 1 && tr[i][j]) {
					int y = j + t[i-1];
					if (y <= T)
						f[i-1][y] = min(f[i-1][y], f[i][j]);
				}
			}
				
		}
		if (f[n][T] == INF)
			printf("Case Number %d: impossible\n", cas);
		else
			printf("Case Number %d: %d\n", cas, f[n][T]);
	}
	return 0;
}