HDU5236(概率DP，贪心)

#include <bits/stdc++.h>
using namespace std;
#define maxn 111111
#define INF 1e20

double dp[maxn], f[maxn];
double p;
int x, n;
double ans;

int main () {
    int t, kase = 0;
    cin >> t;
    while (t--) {
        cin >> n >> p >> x;
        f[0] = 0;
        memset (dp, 0, sizeof dp);
        for (int i = 1; i <= n; i++) {
            f[i] = (f[i-1]+1.0)/(1.0-p);
        }
        ans = INF;
        for (long long i = 1; i <= n; i++) {
            long long j = n/i, k = n-j*i;
            dp[i] = x*i + f[j+1]*k + f[j]*(i-k);
            ans = min (ans, dp[i]);
        }
        printf ("Case #%d: %.6lf\n", ++kase, ans);
    }
    return 0;
}
/*
10
10 0.5 0
*/