noip2006 能量项链

做noip水题- -

得练dp

先找找信心

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
int a[1000];
int f[1000][1000];
int main()
{
    int n;
    cin>>n;
    for (int i=1;i<=n;i++)
    {
        cin>>a[i];
        a[i+n]=a[i];
    }
    for (int l=2;l<=n;l++)
      for (int i=1;i<=2*n;i++)
        for (int j=i+1;j<=i+l-1;j++)
          f[i][i+l-1]=max(f[i][i+l-1],a[j]*a[i]*a[i+l]+f[i][j-1]+f[j][i+l-1]);
    int ans=0;
    for (int i=1;i<=n;i++)
      ans=max(ans,f[i][i+n-1]);
    cout<<ans;
}