水DP。精度很坑。

1 /* hdoj 1903 */ 2 #include 
     
       3 #include 
      
        4 #include 
       
         5 #include 
        
          6  7 #define MAXN 505 8  9 double a[MAXN];10 double dp[MAXN][2];11 12 double max(double a, double b) {13     return a>b ? a:b;14 }15 16 inline double cal(double x, double f) {17     return floor(x*f*0.97*100.)/100.0;18 }19 20 int main() {21     int t, n;22     int i, j, k;23     double tmp;24     25     #ifndef ONLINE_JUDGE26         freopen("data.in", "r", stdin);27     #endif28     29     while (scanf("%d", &n)!=EOF && n) {30         for (i=1; i<=n; ++i)31             scanf("%lf", &a[i]);32         dp[0][0] = 0.0;33         dp[0][1] = 1000.0;34         for (i=1; i<=n; ++i) {35             dp[i][0] = max(dp[i-1][0], cal(dp[i-1][1], 1./a[i]));36             dp[i][1] = max(dp[i-1][1], cal(dp[i-1][0],    a[i]));37         }38         printf("%.2lf\n", dp[n][1]);39     }40     41     return 0;42 }