POJ - 3186 Treats for the Cows（dp）

#include<cstdio>
#include<iostream>
#include<algorithm>
#define debug(X) cout << "[" << #x <<": " << (X) <<"]"<< endl
#define pii pair<int,int>
#define clr(a,b) memset((a),b,sizeof(a))
#define rep(i,a,b) for(int i = a;i < b;i ++)
#define pb push_BACk
#define MP make_pair
#define LL long long
#define ull unsigned LL
#define ls i << 1
#define rs (i << 1) + 1
#define INT(t) int t; scanf("%d",&t)

using namespace std;

const int maxn = 2e3 + 10;
int dp[maxn][maxn];
int a[maxn];

int main() {
    int n;
    while(~scanf("%d",&n)){
        for(int i = 1;i <= n;++ i)
            scanf("%d",&a[i]);
        dp[1][0] = a[1];
        dp[0][1] = a[n];
        rep(i,2,n + 1) dp[i][0] = dp[i - 1][0] + a[i] * i;
        rep(i,n + 1) dp[0][i] = dp[0][i - 1] + a[n - i + 1] * i;
        for(int i = 1;i <= n;++ i)
            for(int j = 1;j <= n;++ j)
                dp[i][j] = max(dp[i - 1][j] + a[i] * (i + j),dp[i][j - 1] + a[n - j + 1] * (i + j));
        int ans = 0;
        for(int i = 0;i <= n;++ i)
            ans = max(ans,dp[i][n - i]);
        cout << ans << endl;
    }
    return 0;
}