poj 1005 I Think I Need a Houseboat

题目描述：

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.) 

分析：

由给出的坐标点可以算出经过这个坐标点的半圆的面积，根据这个面积除以大陆每年缩减的面积就可以算出多少年后可以淹没到房屋。

import java.text.DecimalFormat;import java.util.Scanner;public class Main {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);double result=0.00;int num=0;while(num<12){num++;double i = scanner.nextDouble();result+=i;}  DecimalFormat r=new DecimalFormat("#0.00");  System.out.println("$"+r.format(result/12.00));}}