UVa1025 A Spy in the Metro(dp)

分析：

紫书 P267

AC代码：

#include <iostream>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <vector>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include<list>
#include <bitset>
#include <climits>
#include <algorithm>
#define mset(a,x) memset(a,x,sizeof(a))
#define gcd(a,b) __gcd(a,b)
#define FIN freopen("input","r",stdin)
#define FOUT freopen("output","w",stdout)
typedef long long LL;
const LL mod=1e9+7;
const int INF=0x3f3f3f3f;
const double PI=acos(-1.0);
using namespace std;
int a[500];// 起点发车时刻
int b[500];// 终点发车时刻
int Time[500];// 车站到车站之间的距离
int dp[500][500];
int judge[500][500][10];
int main (){
int n,T,M1,Me;
int cc=1;
//FIN;
while (scanf ("%d",&n)&&n){
mset(Time,0);mset(judge,0);
scanf ("%d",&T);
for (int i=1;i<n;i++) scanf ("%d",&Time[i]);
scanf ("%d",&M1);// 起点
for (int i=1;i<=M1;i++) scanf ("%d",&a[i]);
scanf ("%d",&Me);// 终点
for (int i=1;i<=Me;i++) scanf ("%d",&b[i]);
for (int i=1;i<=M1;i++){// 起点到终点有车的车站时刻
int tt=a[i];
judge[tt][1][0]=1;
for (int j=1;j<n;j++){
judge[tt+=Time[j]][j+1][0]=1;
}
}
for (int i=1;i<=Me;i++){// 终点到起点有车的车站时刻
int tt=b[i];
judge[tt]
[1]=1;
for (int j=n-1;j>=1;j--){
judge[tt+=Time[j]][j][1]=1;
}
}
for (int i=0;i<=T;i++)
for (int j=0;j<=n;j++) dp[i][j]=INF;
for (int i=0;i<=n;i++) dp[i][n+1]=dp[i][0]=0;
dp[0][1]=0;
for (int i=1;i<=T;i++){
for (int j=1;j<=n;j++){
dp[i][j]=dp[i-1][j]+1;
if(j>1&&judge[i][j][0]&&i>=Time[j-1])// 从左向右
dp[i][j]=min(dp[i][j],dp[i-Time[j-1]][j-1]);
if(j<n&&judge[i][j][1]&&i>=Time[j])// 从右向左
dp[i][j]=min(dp[i][j],dp[i-Time[j]][j+1]);
}
}
printf ("Case Number %d: ",cc++);
if (dp[T]
>=INF)printf ("impossible\n");
else printf ("%d\n",dp[T]
);
}
return 0;
}