poj1179

 1 //Accepted    244 KB    0 ms
 2 //区间dp
 3 //石子合并模型
 4 #include <cstdio>
 5 #include <cstring>
 6 #include <iostream>
 7 using namespace std;
 8 const int imax_n = 105;
 9 const int Pinf = 100000000;
10 const int Ninf = -100000000;
11 int dp_min[imax_n][imax_n];
12 int dp_max[imax_n][imax_n];
13 int a[imax_n];
14 char s[imax_n][3];
15 int n;
16 int max(int a,int b)
17 {
18     return a>b?a:b;
19 }
20 int min(int a,int b)
21 {
22     return a<b?a:b;
23 }
24 int cal(int a,int b,char s[])
25 {
26     if (s[0]==‘t‘) return a+b;
27     return a*b;
28 }
29 void Dp()
30 {
31     for (int i=1;i<2*n;i++)
32     dp_max[i][i]=dp_min[i][i]=a[i];
33     for (int l=2;l<=n;l++)
34     {
35         for (int i=1;i<2*n;i++)
36         {
37             int j=i+l-1;
38             if (j>=2*n) break;
39             dp_max[i][j]=Ninf;
40             dp_min[i][j]=Pinf;
41             for (int k=i;k<=j-1;k++)
42             {
43                 dp_max[i][j]=max(dp_max[i][j],cal(dp_max[i][k],dp_max[k+1][j],s[k+1]));
44                 dp_max[i][j]=max(dp_max[i][j],cal(dp_min[i][k],dp_min[k+1][j],s[k+1]));
45                 dp_min[i][j]=min(dp_min[i][j],cal(dp_min[i][k],dp_min[k+1][j],s[k+1]));
46                 dp_min[i][j]=min(dp_min[i][j],cal(dp_max[i][k],dp_min[k+1][j],s[k+1]));
47                 dp_min[i][j]=min(dp_min[i][j],cal(dp_min[i][k],dp_max[k+1][j],s[k+1]));
48             }
49         }
50     }
51     int ans=Ninf;
52     for (int i=1;i<=n;i++)
53     ans=max(ans,dp_max[i][i+n-1]);
54     printf("%d\n",ans);
55     int flag=0;
56     for (int i=1;i<=n;i++)
57     {
58         if (dp_max[i][i+n-1]==ans)
59         {
60             if (flag==0)
61             {
62                 printf("%d",i);
63                 flag=1;
64             }
65             else
66             {
67                 printf(" %d",i);
68             }
69         }
70     }
71     printf("\n");
72 }
73 int main()
74 {
75     while (scanf("%d",&n)!=EOF)
76     {
77         for (int i=1;i<=n;i++)
78         scanf("%s%d",s[i],&a[i]);
79         for (int i=1;i<n;i++)
80         {
81             a[n+i]=a[i];
82             strcpy(s[n+i],s[i]);
83         }
84         Dp();
85     }
86     return 0;
87 }