紫书第九章-A - A Spy in the Metro

A - A Spy in the Metro 点击打开链接

参考自https://www.cnblogs.com/zzy19961112/p/5877436.html#undefined

/*
 *dp[i][j]表示时刻i，在车站j，最少还需要等待多长时间
 *has_train[t][i][0]表示时刻t，在车站i是否有向右开的火车
 *has_train[t][i][1]表示时刻t，在车站i是否有向左开的火车
 */
#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int maxn = 55;
const int maxt = 205;
const int INF = 0x3f3f3f3f;
int t[maxn],has_train[maxt][maxn][2],dp[maxt][maxn];
int main()
{
    int n,Case = 0;
    while (~scanf("%d",&n) && n)
    {
        int T,M1,M2,d;
        memset(has_train,0,sizeof(has_train));
        memset(dp,0,sizeof(dp));
        scanf("%d",&T);
        for (int i = 1;i < n;i++)    scanf("%d",&t[i]);
        scanf("%d",&M1);
        while (M1--)
        {
            scanf("%d",&d);
            for (int j = 1;j < n;j++)
            {
                if (d <= T)  has_train[d][j][0] = 1;
                d += t[j];
            }
        }
        scanf("%d",&M2);
        while (M2--)
        {
            scanf("%d",&d);
            for (int j = n - 1;j > 0;j--)
            {
                if (d <= T)  has_train[d][j+1][1] = 1;
                d += t[j];
            }
        }
        for (int i = 1;i < n;i++)    dp[T][i] = INF;
        dp[T][n] = 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 && has_train[i][j][0] && i + t[j] <= T) dp[i][j] = min(dp[i][j],dp[i+t[j]][j+1]);
                if (j > 1 && has_train[i][j][1] && i + t[j-1] <= T)   dp[i][j] = min(dp[i][j],dp[i+t[j-1]][j-1]);
            }
        }
        printf("Case Number %d: ",++Case);
        dp[0][1]>=INF ? printf("impossible\n"):printf("%d\n",dp[0][1]);
    }
    return 0;
}