题目链接 Treats for the Cows
直接区间DP就好了，用记忆化搜索是很方便的。
1 #include <cstdio> 2 #include <cstring> 3 #include <iostream> 4 #include <algorithm> 5 6 using namespace std; 7 8 #define rep(i,a,b) for(int i(a); i <= (b); ++i) 9 #define LL long long 10 11 12 13 const int Q = 2000 + 10; 14 15 LL f[Q][Q]; 16 LL a[Q]; 17 int n; 18 int s[Q]; 19 int c[Q][Q]; 20 21 LL dp(int i, int j, LL k){ 22 if (i == j) return a[i] * k; 23 if (f[i][j] != -1) return f[i][j]; 24 LL ret = -100000000000LL; 25 ret = max(ret, a[i] * k + dp(i + 1, j, k + 1)); 26 ret = max(ret, a[j] * k + dp(i, j - 1, k + 1)); 27 return f[i][j] = ret; 28 } 29 30 31 int main(){ 32 33 34 while(~scanf("%d", &n)){ 35 rep(i, 1, n) scanf("%lld", a + i); 36 memset(f, -1, sizeof f); 37 printf("%lld ", dp(1, n, 1LL)); 38 } 39 40 return 0; 41 42 }