POJ2355 Railway tickets DP优化

　　简单的DP，转移方程：f[i][j]=Min { f[i][k] + C(n) }，注意到f[i][j]是单调递增的，用二分搜索优化即可。注意到此题有个trick，那就是s>e!!!

 1 //STATUS:C++_AC_16MS_252KB
 2 #include<stdio.h>
 3 #include<stdlib.h>
 4 #include<string.h>
 5 #include<math.h>
 6 #include<iostream>
 7 #include<string>
 8 #include<algorithm>
 9 #include<vector>
10 #include<queue>
11 #include<stack>
12 #include<map>
13 using namespace std;
14 #define LL __int64
15 #define pii pair<int,int>
16 #define Max(a,b) ((a)>(b)?(a):(b))
17 #define Min(a,b) ((a)<(b)?(a):(b))
18 #define mem(a,b) memset(a,b,sizeof(a))
19 #define lson l,mid,rt<<1
20 #define rson mid+1,r,rt<<1|1
21 const int N=10010,INF=0x3f3f3f3f,MOD=1000000007;
22 const double DNF=100000000000;
23 
24 int d[N];
25 LL f[N];
26 int l1,l2,l3,c1,c2,c3,n,s,e;
27 
28 LL binary(int low,int i,int cost)
29 {
30     int l=s,r=i,mid;
31     while(l<r)
32     {
33         mid=(l+r)>>1;
34         if(d[mid]>=low)r=mid;
35         else l=mid+1;
36     }
37     return f[l]+cost;
38 }
39 
40 int main()
41 {
42  //   freopen("in.txt","r",stdin);
43     int i,j,t;
44     while(~scanf("%d%d%d%d%d%d",&l1,&l2,&l3,&c1,&c2,&c3))
45     {
46         mem(f,INF);
47         scanf("%d%d%d",&n,&s,&e);
48         for(i=2;i<=n;i++)
49             scanf("%d",&d[i]);
50         if(s>e)t=s,s=e,e=t;
51 
52         f[s]=0;
53         for(i=s+1;i<=e;i++){
54             t=d[i]-l1;
55             f[i]=Min(f[i],binary(t,i,c1));
56             t=d[i]-l2;
57             f[i]=Min(f[i],binary(t,i,c2));
58             t=d[i]-l3;
59             f[i]=Min(f[i],binary(t,i,c3));
60         }
61 
62         printf("%I64d\n",f[e]);
63     }
64     return 0;
65 }