POJ3086 Treats for the Cows(区间DP)

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。

 #include <cstdio>
 #include <cstring>
 #include <iostream>
 #include <algorithm>

 using namespace std;

 #define rep(i,a,b) for(int i(a); i <= (b); ++i)
 #define LL  long long

 const int Q     =            +       ;

 LL f[Q][Q];
 LL a[Q];
 int n;
 int s[Q];
 int c[Q][Q];

 LL dp(int i, int j, LL k){
     if (i == j) return a[i] * k;
     if (f[i][j] != -) return f[i][j];
     LL ret = -100000000000LL;
     ret = max(ret, a[i] * k + dp(i + , j, k + ));
     ret = max(ret, a[j] * k + dp(i, j - , k + ));
     return f[i][j] = ret;
 }

 int main(){

     while(~scanf("%d", &n)){
         rep(i, , n) scanf("%lld", a + i);
         memset(f, -, sizeof f);
         printf("%lld\n", dp(, n, 1LL));
     }

     return ;

 }