hdu5984——Pocky（数学期望）

Problem Description
Let’s talking about something of eating a pocky. Here is a Decorer Pocky, with colorful decorative stripes in the coating, of length L.
While the length of remaining pocky is longer than d, we perform the following procedure. We break the pocky at any point on it in an equal possibility and this will divide the remaining pocky into two parts. Take the left part and eat it. When it is not longer than d, we do not repeat this procedure.
Now we want to know the expected number of times we should repeat the procedure above. Round it to 6 decimal places behind the decimal point.

Input
The first line of input contains an integer N which is the number of test cases. Each of the N lines contains two float-numbers L and d respectively with at most 5 decimal places behind the decimal point where 1 ≤ d, L ≤ 150.

Output
For each test case, output the expected number of times rounded to 6 decimal places behind the decimal point in a line.

Sample Input
6
1.0 1.0
2.0 1.0
4.0 1.0
8.0 1.0
16.0 1.0
7.00 3.00

Sample Output
0.000000
1.693147
2.386294
3.079442
3.772589
1.847298

网上为数不多的解答都是找规律出来的。。。样例答案减去1后，1.386294是0.689147的两倍，2.079442是它的三倍，然后猜出和2的对数有关，而且还是以e为底的。。。。仰望高端玩家

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#define INF 0x3f3f3f3f
#define MAXN 100010
#define Mod 10001
using namespace std;
int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        double l,d;
        scanf("%lf%lf",&l,&d);
        if(l<=d)
            printf("0.000000\n");
        else
            printf("%.6lf\n",log(l/d)+1);
    }
    return 0;
}