【HDOJ】1903 Exchange Rates

水DP。精度很坑。

/* hdoj 1903 */
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>

#define MAXN 505

double a[MAXN];
double dp[MAXN][2];

double max(double a, double b) {
    return a>b ? a:b;
}

inline double cal(double x, double f) {
    return floor(x*f*0.97*100.)/100.0;
}

int main() {
    int t, n;
    int i, j, k;
    double tmp;
    
    #ifndef ONLINE_JUDGE
        freopen("data.in", "r", stdin);
    #endif
    
    while (scanf("%d", &n)!=EOF && n) {
        for (i=1; i<=n; ++i)
            scanf("%lf", &a[i]);
        dp[0][0] = 0.0;
        dp[0][1] = 1000.0;
        for (i=1; i<=n; ++i) {
            dp[i][0] = max(dp[i-1][0], cal(dp[i-1][1], 1./a[i]));
            dp[i][1] = max(dp[i-1][1], cal(dp[i-1][0],    a[i]));
        }
        printf("%.2lf
", dp[n][1]);
    }
    
    return 0;
}