# Nature Reserve (three points)

## Sol

I want to cry without tears.... Last night, it must have been Zhixi. qwq

Say something different from the standard calculation..

Obviously, the \ (x \) axis can be divided into three parts and the radius can be divided into two parts.

Congratulations on getting a TLE..

Then the second two-dimensional bisection is unnecessary. Take the standard equation of circle and push it to get a maximum value..... Last night, I didn't expect that qwq humiliated the math teacher..

```#include<cstdio>
#include<cmath>
#include<algorithm>
#define double long double
using namespace std;
const double eps = 1e-7, INF = 1e18;
const int MAXN = 1e5 + 10;
char c = getchar(); int x = 0, f = 1;
while(c < '0' || c > '9') {if(c == '-') f = -1; c = getchar();}
while(c >= '0' && c <= '9') x = x * 10 + c - '0',c = getchar();
return x * f;
}
int N, up, down;
double max(double a, double b) {return a > b ? a : b;}
double min(double a, double b) {return a < b ? a : b;}
struct Node {
double x, y;
}a[MAXN];
int check(int x, int y) {
if(x < 0 && y > 0) return 1;
else return 0;
}
double mxr;
double sqr(double x) {
return x * x;
}
double f(double x) {
double mx = 0;
for(int i = 1; i <= N; i++)
mx = max(mx, fabs((sqr(a[i].x - x) + sqr(a[i].y)) / (2.0 * a[i].y)));
return mx;
}

int main() {
double L = INF, R = -INF;
for(int i = 1; i <= N; i++) {
up = min(up, a[i].y);
mxr = max(a[i].y, mxr);
L = min(a[i].x, L);
R = max(a[i].x, R);
}
if(check(up, mxr)) {puts("-1"); return 0;}
mxr = INF;
if(up < 0) for(int i = 1; i <= N; i++) a[i].y = -a[i].y;
int tim = 100;
while(tim--) {
double x = (2 * L + R) / 3, y = (L + 2 * R) / 3;
f(x) < f(y) ? R = y : L = x;
//  printf("%Lf %Lf\n", f(x), f(y));
}
printf("%.10Lf", f(L));
return 0;
}```

Keywords: C++

Added by rwwd on Thu, 19 Dec 2019 22:48:08 +0200