嗯...

 

题目链接：https://www.luogu.org/problem/P1880

 

这道题特点在于石子是一个环，所以让a[i+n] = a[i]（两倍长度）即可解决环的问题，然后注意求区间最小值的时候dp要初始化为一个很大的数...

 

AC代码：

1 #include
      
        2 #include
       
         3 #include
        
          4 #include
         
           5  6 using namespace std; 7  8 int dp1[205][205], dp2[205][205], sum[205], a[205]; 9 10 int main(){11     int n;12     scanf("%d", &n);13     for(int i = 1; i <= n; i++) {scanf("%d", &a[i]); a[i + n] = a[i];}14     for(int i = 1; i <= n * 2; i++) {sum[i] = sum[i - 1] + a[i];}15     for(int l = 1; l <= n; l++){16         for(int i = 1; i <= 2 * n; i++){17             int j = i + l;18             dp2[i][j] = 0x3f3f3f;// 求最小值初始化为很大 19             if(j > 2 * n) break;20             for(int k = i; k < j; k++){21                 dp1[i][j] = max(dp1[i][j], dp1[i][k] + dp1[k + 1][j] + sum[j] - sum[i - 1]);22                 dp2[i][j] = min(dp2[i][j], dp2[i][k] + dp2[k + 1][j] + sum[j] - sum[i - 1]);23             }24         }25     }26     int maxx = 0, minn = 0x3f3f;27     for(int i = 1; i <= n; i++){28         int j = i + n - 1;29         maxx = max(maxx, dp1[i][j]);30         minn = min(minn, dp2[i][j]);31     }32     printf("%d\n%d\n", minn, maxx);33     return 0;34 }