20分求调啊啊啊啊啊
```cpp
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
using namespace std;
#include <vector>
#include <set>
#include <map>
#include <cstdio>
#include <cstring>
#include <queue>
#include <cstdlib>
#include <algorithm>
#include <list>
#include <string>
#include <cmath>
#include <bitset>
#include <stack>
#include <functional>
#include <unordered_map>
#include <unordered_set>
#define ull unsigned long long
#define ll long long
#define pii pair<ll ,ll>
#define ft first
#define sd second
#define cy cout<<"YES"<<endl
#define cn cout<<"NO"<<endl
#define forn(i,n) for(ll (i)=0;(i)<(n);(i)++)
#define forne(i,n) for(ll (i)=1;(i)<=(n);(i)++)
#define rforn(i,n) for(ll (i)=(n-1);i>=0;i--)
#define rforne(i,n) for(ll (i)=n;i>=1;i--)
#define vv vector
#define inf32 INT32_MAX
#define inf64 INT64_MAX
#define LD double
#define PI acos(-1)
#define debug(a,b) cout<<a<<b
#define eps 1e-10
const int N = 4e5 + 100;
const int mod = 998244353;
ll T;
LD a;
//点类
struct Point {
LD x, y;
Point(LD x, LD y) { this->x = x; this->y = y; }
Point() {}
#define line Point
//点的加减乘运算
Point operator+(Point b) { return Point(this->x + b.x, this->y + b.y); }
Point operator-(Point b) { return Point(this->x - b.x, this->y - b.y); }
Point operator*(LD t) { return Point(this->x * t, this->y * t); }
LD operator*(Point b) { return this->x * b.x + this->y * b.y; }
bool operator==(Point b) { return this->x == b.x && this->y == b.y; }
Point operator/(LD t) { return { this->x / t, this->y / t }; }
};
struct Line {
Point s, e;
ll id;
bool operator==(Line b) {
return this->e == b.e && this->s == b.s;
}
};
struct Circle { Point p; LD r; };
class Geomtry_tool {
public:
//求长度
static LD len(line a) { return sqrt(a.x * a.x + a.y * a.y); }
//求两点距离
LD dis(Point a, Point b) { return sqrt((a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y)); }
//两个向量求角度，使用的是余弦定理求arccos
static LD angle(line a, line b) { return acos(a * b / len(a) / len(b)); }
//两个向量求叉积
static LD cross(line a, line b) { return a.x * b.y - a.y * b.x; }
//epslion，判断是否等于0
static int sgn(LD x) { return fabs(x) <= eps ? 0 : x > 0 ? 1 : -1; }
//防止负0的发生
static void zero(Point& a) { if (fabs(a.x) <= eps)a.x = 0; if (fabs(a.y) <= eps)a.y = 0; }
//可以用来判断c在b的左侧还是右侧
//大于0，c在ab左侧；小于0，c在ab右侧；等于0，三点共线
static LD cross(Point a, Point b, Point c) { return cross(b - a, c - a); }
//三点点积ab*ac
static LD dot(Point a, Point b, Point c) { return (b - a) * (c - a); }
//判断直线与线段的交点情况，在同侧则无交点；
//如果是判断线段与线段有无交点，则需要分别设ab，cd为直线，进行两次判断
static bool l_S_inter(Point a, Point b, Point c, Point d) {
return sgn(cross(a, b, c) * cross(a, b, d)) <= 0;//直线与线段
}
//线段与线段
static bool S_S_inter(Point a, Point b, Point c, Point d) {
return l_S_inter(a, b, c, d) && l_S_inter(c, d, a, b);
}
//求两直线的交点
static Point getNode(Point a, line u, Point b, line v) {
LD t = cross((a - b), v) / cross(v, u);//求面积之比
return a + u * t;
}
//逆时针旋转b
static Point rotate(Point a, LD b) { //将某点绕原点逆时针旋转b角度
return { a.x * cos(b) - a.y * sin(b), a.x * sin(b) + a.y * cos(b) };
}
//求多边形面积
static LD get_S(vv<Point>& p) {
int k = p.size() - 1; LD res = 0;
for (int i = 2; i < k; i++)
res += cross((p[i] - p[1]), (p[i + 1] - p[1]));
return res / 2;
}
//求中垂线
static Line midperp(Point a, Point b) {
return { (a + b) / 2,rotate(b - a, PI / 2) };
}
};
//最小圆覆盖
class Minimum_circle {
public:
Geomtry_tool fn; Circle C;
//求两点共圆
Circle cover(Point a, Point b) {
return { (a + b) / 2,fn.dis(a,b) / 2 };
}
Point cross(Line a, Line b) {//求ab两线交点
return fn.getNode(a.e, a.s-a.e, b.e, b.s-b.e);
}
//求三点共圆
Circle cover(Point a, Point b, Point c) {
Line u = fn.midperp(a, b), v = fn.midperp(a, c);
Point p = cross(u, v);
return { p,fn.dis(p,a) };
}
//增量法
void increment(vv<Point>& p) {
C = { p[1], 0 };
int n = p.size() - 1;
for (int i = 2; i <= n; i++) {
if (C.r < fn.dis(C.p, p[i])) {
C = { p[i], 0 }; //一点圆
for (int j = 1; j < i; j++) {
if (C.r < fn.dis(C.p, p[j])) {
C = cover(p[i], p[j]); //两点圆
for (int k = 1; k < j; k++)
if (C.r < fn.dis(C.p, p[k]))
C = cover(p[i], p[j], p[k]); //三点圆
}
}
}
}
}
};
void solve() {
int n; cin >> n;
vv<Point>nums(n + 1);
forne(i, n)
cin >> nums[i].x >> nums[i].y;
random_shuffle(nums.begin() + 1 ,nums.end()); //随机化
Minimum_circle mc;
mc.increment(nums);
printf("%.10lf\n%.10lf %.10lf\n", mc.C.r, mc.C.p.x, mc.C.p.y);
}
int main() {
//std::ios::sync_with_stdio(false);
T = 1;
//cin >> T;
while (T--)
solve();
}
```
by Exile_Code @ 2024-01-28 23:02:20