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Polygon POJ - 1179

除了维护一个区间最大值，还要一个最小值，( 有负数)

#include <iostream>
#include <algorithm>
#include <cstring>
using namespace std ;
 const int N=160;
  
 #define inf 1e9
 int n,a[N],f[N][N],g[N][N];
 char op[N] ;
  
  
 signed main(){
     int i,j,k;
     cin>>n;
     for(i=1;i<=n;i++){
        cin>>op[i]>>a[i],a[i+n]=a[i],op[i+n]=op[i];
     }
     for(i=1;i<=n*2;i++)
      for(j=1;j<=n*2;j++) f[i][j]=-inf,g[i][j]=inf;
     for(i=1;i<=n*2;i++) f[i][i]=g[i][i]= a[i];
      
     for(int len=2;len<=n;len++)
      for(i=1;i+len-1<=2*n;i++){
        j=i+len-1;
        for(k=i;k<j;k++){
            if(op[k+1]=='t'){
                f[i][j]= max(f[i][j],f[i][k]+f[k+1][j]);
                g[i][j]= min(g[i][j], g[i][k]+g[k+1][j]);
            }
            else{
                f[i][j]=max(f[i][j],max(f[i][k]*f[k+1][j],
                max(f[i][k]*g[k+1][j],max(g[i][k]*f[k+1][j],
                g[i][k]*g[k+1][j]))));
                 
                g[i][j]=min(g[i][j],min(f[i][k]*f[k+1][j],
                min(f[i][k]*g[k+1][j],min(g[i][k]*f[k+1][j],
                g[i][k]*g[k+1][j]))));
            }
        }
      }
      int ans= -inf;
      for(i=1;i<=n;i++)  ans=max(ans,f[i][i+n-1]);
      cout<<ans<<endl;
      for(i=1;i<=n;i++) if(f[i][i+n-1]==ans) cout<<i<<' ';
 }