zoj1242——Carbon Dating
本来是一道很简单的模拟题，纯数学运算，但是竟然WA了三次！！！最后发现是samples之间需要隔一行！可是为什么不是格式错误呢？细心啊。
题目大意就是考古学上根据C12这种同位素的衰减速率来推断一些化石的年代。需要我们通过编程根据carbon的数量w和检测到的衰减速率d来估算产生的年代；数据的处理上需要把10000以下的化为100的整数倍，将10000以上的化为1000的整数倍（通过整形数运算特征很容易得出啦）；最后要注意输出是例子之间空一行！
Until the second half of the 20th century, determining the actual age of an archaeological find had been more or less a matter of educated guessing. Comparing finds to previous, already dated, ones and evaluation of the surroundings of a find were the best available techniques.
But nowadays, there is a much more reliable method: carbon dating. Carbon dating works as follows: Naturally occurring carbon is a mixture of stable isotope (mostly 12C) and the unstable, radioactive, isotope 14C. The ratio between the two is almost constant in living organisms: 14C slowly decays, but at the same time, the radiation of the sum produces the same amount in the upper atmosphere, which is taken in by the organisms.
But when, for example, a tree is felled and made to wood, it does not receive any new 14C, and the amount present in the wood becomes less and less due to radioactive decay. In this problem, you are to write a program that uses information about the amount of remaining 14C to determine the approximate age of sample. The following facts must be used:
The amount of 14C present in a sample halves every 5730 years (this is called the half-life of 14C).
The rate of decay (measured in decays per hour per gram of carbon) is proportional to the amount of 14C left in the sample.
In living organisms (age zero), there are 810 decays per hour per gram of carbon.
So, for example, if we measure in a sample of one gram of carbon 405 decays per hour, we know that it is approximately 5730 years old.
Input
The input contains the measurements taken of several samples we want to date. Every line contains two positive integers, w and d. w is the amount of carbon in the sample, measured in grams, and d is the number of decays measured over one hour.
The input is terminated by a test case starting with w = d = 0.
Output
For each sample description in the input, first output the numnber of the sample, as shown in the sample output.Then print the approximate age in the format
The approximate age is x years.
If the age is less than 10,000 years, x should be rounded to the colsest multiple of 100 years (rounding up in case of a tie). If the age is more than 10,000 years, round it to the closest multiple of 1000 years (again rounding up in case of a tie).
Print a blank line after each sample.
Sample Input
1 405
5 175
0 0
Sample Output
Sample #1
The approximate age is 5700 years.
Sample #2
The approximate age is 26000 years.
#include
#include
using namespace std;
int main()
{
int w,d;
int count=1;
while(cin>>w>>d&&(w>0&&d>0))
{
double y=log(810.0*w/d)/log(2);
int year = (int)(5730*y);
if(year<10000)
{
cout<<"Sameple #"<