POJ 1006 I Think I Need a Houseboat（二分）

二分满足条件的年数。

代码：

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
#include <cmath>
#define eps 1e-8
#define pi acos(-1.0)
int BS(double k){
	int l=0,r=100000;
	int mid;
	while(l<r-1){
		mid=(l+r)/2;
		double t=sqrt(mid*100.0/pi);
		if(t>k-eps) r=mid;
		else l=mid;
	}
	return r;
}
int main(){
	int N;
	scanf("%d",&N);
	for(int i=1;i<=N;i++){
		double x,y;
		scanf("%lf%lf",&x,&y);
		int res=BS(sqrt(x*x+y*y));
		printf("Property %d: This property will begin eroding in year %d.\n",i,res);
	}
	printf("END OF OUTPUT.\n");
}