1 /*I Think I Need a Houseboat
 2 时间限制：1000 ms  |  内存限制：65535 KB 
 3 难度：1
 4 描述 
 5 Fred Mapper is considering purchasing some land in Louisiana to build his house on. In the process of investigating the land, he learned 
 6 that the state of Louisiana is actually shrinking by 50 square miles each year, due to erosion caused by the Mississippi River. Since Fred is 
 7 hoping to live in this house the rest of his life, he needs to know if his land is going to be lost to erosion. 
 8 After doing more research, Fred has learned that the land that is being lost forms a semicircle. This semicircle is part of a circle centered
 9  at (0,0), with the line that bisects the circle being the X axis. Locations below the X axis are in the water. The semicircle has an area of 0 
10  at the beginning of year 1. (Semicircle illustrated in the Figure.) 
11 输入
12 The first line of input will be a positive integer indicating how many data sets will be included (N). Each of the next N lines will contain the
13  X and Y Cartesian coordinates of the land Fred is considering. These will be floating point numbers measured in miles. The Y coordinate will 
14  be non-negative. (0,0) will not be given.
15 输出
16 For each data set, a single line of output should appear. This line should take the form of: “Property N: This property will begin eroding in 
17 year Z.” Where N is the data set (counting from 1), and Z is the first year (start from 1) this property will be within the semicircle AT THE END 
18 OF YEAR Z. Z must be an integer. After the last data set, this should print out “END OF OUTPUT.”
19 样例输入
20 2
21 1.0 1.0
22 25.0 0.0样例输出
23 Property 1: This property will begin eroding in year 1.
24 Property 2: This property will begin eroding in year 20.
25 END OF OUTPUT.
26 
27 hint
28 1.No property will appear exactly on the semicircle boundary: it will either be 
29 inside or outside. 
30 2.This problem will be judged automatically. Your answer must match exactly, 
31 including the capitalization, punctuation, and white-space. This includes the periods 
32 at the ends of the lines. 
33 3.All locations are given in miles.
34 来源
35 POJ
36 上传者
37 iphxer
38 */
39 #include<stdio.h>
40 #include<math.h>
41 #define pi 3.1415926
42 int main()
43 {
44     float x, y,  r;
45     int n, i = 1, years;
46     scanf("%d", &n);
47     while(n--)
48     {
49         scanf("%f%f", &x, &y);
50         r = sqrt( x*x + y*y);
51         if( pi*r*r/2.0/50.0 -(int)(pi*r*r/2.0/50.0) <= 0.00000001)//相等时的误差判断 
52         years = (int)(pi*r*r/2.0/50.0);
53         else
54         years = (int)(pi*r*r/2.0/50.0) + 1;
55         printf("Property %d: This property will begin eroding in year %d.\n", i, years);
56         i++;
57     }
58     printf("END OF OUTPUT.\n");
59     return 0;
60 }