洛谷 P1063 能量项链

题目传送门

解题思路：

一道很模板的环形dp,要注意状态转移时串的头和尾到底是哪个.

AC代码:

#include<cstdio>
#include<iostream>

using namespace std;

int n,a[202],f[202][202],ans;

int main()
{
    scanf("%d",&n);
    for(int i = 1;i <= n; i++){
         scanf("%d",&a[i]);
         a[i+n] = a[i];
    }
    for(int p = 1;p < n; p++)
         for(int i = 1,j = i + p;i < n + n && j <= n + n; i++,j = i + p)
            for(int k = i;k < j; k++)
                f[i][j] = max(f[i][j],f[i][k] + f[k+1][j] + a[i] * a[k+1] * a[j+1]);
    for(int i = 1;i <= n; i++)
        ans = max(ans,f[i][i+n-1]);
    printf("%d",ans);
    return 0;
}