bzoj1652

分析：直接dp就好。

#include<cstdio>#include<cstring>#include<algorithm>#include<cmath>#define fo(i,a,b) for(int i=a;i<=b;i++)#define fd(i,a,b) for(int i=a;i>=b;i--)using namespace std;const int N=2e3+5;int n,a[N],f[N][N];int main(){    scanf("%d",&n);    fo(i,1,n)scanf("%d",&a[i]);    fo(k,1,n)    for(int i=1;i+k-1<=n;i++)    {        int t=n-k+1,j=i+k-1;        f[i][j]=max(f[i+1][j]+t*a[i],f[i][j-1]+t*a[j]);    }     printf("%d\n",f[1][n]);}