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HDU 1065 I Think I Need a Houseboat 计算几何[解题报告] C++

I Think I Need a Houseboat

问题描述 :

Fred Mapper is considering purchasing some land in Louisiana to build his house on. In the process of investigating the land, he learned 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 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.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 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 at the beginning of year 1. (Semicircle illustrated in the Figure.)


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 X and Y Cartesian coordinates of the land Fred is considering. These will be floating point numbers measured in miles. The Y coordinate will be non-negative. (0,0) will not be given.


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 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 OF YEAR Z. Z must be an integer.

After the last data set, this should print out “END OF OUTPUT.”


1. No property will appear exactly on the semicircle boundary: it will either be inside or outside.

2. This problem will be judged automatically. Your answer must match exactly, including the capitalization, punctuation, and white-space. This includes the periods at the ends of the lines.

3. All locations are given in miles.


1.0 1.0 
25.0 0.0


Property 1: This property will begin eroding in year 1. 
Property 2: This property will begin eroding in year 20. 

PI设置为3.1415927 WA了一次!

#include <iostream>
#include <cmath>
using namespace std;
const double PI = 3.1415926;

int main()
	int t;
	cin >> t;
	for(int i = 1; i <= t; i++)
		double x, y;
		cin >> x >> y;
		double d = x * x + y * y ;
		double s = 0.5 * PI * d;
		int year = ceil(s / 50.0);
		printf("Property %d: This property will begin eroding in year %d.\n", i, year);
		if(i == t)
			printf("END OF OUTPUT.\n");
	return 0;

  1. 这道题目虽然简单,但是小编做的很到位,应该会给很多人启发吧!对于面试当中不给开辟额外空间的问题不是绝对的,实际上至少是允许少数变量存在的。之前遇到相似的问题也是恍然大悟,今天看到小编这篇文章相见恨晚。

  2. 我还有个问题想请教一下,就是感觉对于新手来说,递归理解起来有些困难,不知有没有什么好的方法或者什么好的建议?