Language: C++

/*
このコード、と～おれ!
Be accepted!
∧＿∧　
（｡･ω･｡)つ━☆・*。
⊂　　 ノ 　　　・゜+.
　しーＪ　　　°。+ *´¨)
 　　　　　　　　　.· ´¸.·*´¨) ¸.·*¨)
		  　　　　　　　　　　(¸.·´ (¸.·'* ☆
					*/

#include <stdio.h>
#include <algorithm>
#include <string>
#include <cmath>
#include <cstring>
#include <vector>
#include <numeric>
#include <iostream>
#include <random>
#include <map>
#include <unordered_map>
#include <queue>
#include <regex>
#include <functional>
#include <complex>
					/*多倍長整数/cpp_intで宣言
					#include <boost/multiprecision/cpp_int.hpp>

					using namespace boost::multiprecision;
					*/

#pragma GCC target ("avx2")
#pragma GCC optimization ("O3")
#pragma GCC optimization ("unroll-loops")
#define rep(i, n) for(int i = 0; i < (n); ++i)
#define rep1(i, n) for(int i = 1; i <= (n); ++i)
#define rep2(i, n) for(int i = 2; i < (n); ++i)
#define repr(i, n) for(int i = n; i >= 0; --i)
#define reprm(i, n) for(int i = n - 1; i >= 0; --i)
#define printynl(a) printf(a ? "yes\n" : "no\n")
#define printyn(a) printf(a ? "Yes\n" : "No\n")
#define printYN(a) printf(a ? "YES\n" : "NO\n")
#define printin(a) printf(a ? "possible\n" : "inposible\n")
#define printdb(a) printf("%.50lf\n", a)//少数出力
#define printdbd(a) printf("%.16lf\n", a)//少数出力(桁少なめ)
#define prints(s) printf("%s\n", s.c_str())//string出力
#define all(x) (x).begin(), (x).end()
#define allsum(a, b, c) ((a + b) * c / 2)//等差数列の和、初項,末項,項数
#define pb push_back
#define priq priority_queue
#define rpriq priq<int, vector<int>, greater<int>>
#define deg_to_rad(deg) (((deg)/360.0)*2.0*PI)
#define rad_to_deg(rad) (((rad)/2.0/PI)*360.0)
#define Please return
#define AC 0
#define addf(T) [](T a, T b){return (a + b);}
#define minf(T) [](T a, T b){return min(a, b);}
#define maxf(T) [](T a, T b){return max(a, b);}


using ll = long long;

constexpr int INF = 1073741823;
constexpr int MINF = -1073741823;
constexpr ll LINF = ll(4661686018427387903);
constexpr ll MOD = 1000000007;
const long double PI = acos(-1.0L);

using namespace std;

void scans(string& str) {
	char c;
	str = "";
	scanf("%c", &c);
	if (c == '\n')scanf("%c", &c);//最初の改行対策
	while (c != '\n' && c != -1) {
		str += c;
		scanf("%c", &c);
	}
}

void scanc(char& str) {
	char c;
	scanf("%c", &c);
	if (c == -1)return;
	while (c == '\n') {
		scanf("%c", &c);
	}
	str = c;
}

double acot(double x) {
	return PI / 2 - atan(x);
}

ll gcd(ll a, ll b) {
	if (b == 0) return a;
	return gcd(b, a % b);
}

ll lcm(ll number1, ll number2) {//lcmを求める
	return number1 / gcd(number1, number2) * number2;
}

ll LSB(ll n) { return (n & (-n)); }

/*-----------------------------------------ここからコード-----------------------------------------*/

const double EPS = 1e-8;
typedef complex<double> P;
namespace std {
	bool operator < (const P& a, const P& b) {
		return real(a) != real(b) ? real(a) < real(b) : imag(a) < imag(b);
	}
}
double cross(const P& a, const P& b) {
	return imag(conj(a) * b);
}
double dot(const P& a, const P& b) {
	return real(conj(a) * b);
}

struct L : public vector<P> {
	L(const P& a, const P& b) {
		push_back(a); push_back(b);
	}
};

typedef vector<P> G;

struct C {
	P p; double r;
	C(const P& p, double r) : p(p), r(r) { }
};

#include <valarray>

typedef double number;
typedef valarray<number> point;
const int dim = 3;

number dot(const point& a, const point& b) {
	return (a * b).sum();
}
point cross(const point& a, const point& b) {
	return a.cshift(+1) * b.cshift(-1)
		- a.cshift(-1) * b.cshift(+1);
}
number dist2(const point& a, const point& b) {
	return dot(a - b, a - b);
}

struct min_ball {
	point center;
	number radius2;
	void add(const point& p) {
		ps.push_back(p);
	}
	void compile() {
		m = 0;
		center.resize(dim, 0);
		radius2 = -1;
		make_ball(ps.end());
	}
	template <class OUT>
	void support(OUT out) {
		copy(ps.begin(), supp_end, out);
	}
	min_ball() {
		for (int i = 0; i <= dim; ++i) {
			c[i].resize(dim, 0);
			v[i].resize(dim, 0);
		}
	}
private:
	list<point> ps;
	list<point>::iterator supp_end;
	int m;
	point v[dim + 1], c[dim + 1];
	number z[dim + 1], r[dim + 1];
	void pop() { --m; }
	void push(const point& p) {
		if (m == 0) {
			c[0] = p; r[0] = 0;
		}
		else {
			number e = dist2(p, c[m - 1]) - r[m - 1];
			point delta = p - c[0];
			v[m] = p - c[0];
			for (int i = 1; i < m; ++i)
				v[m] -= v[i] * dot(v[i], delta) / z[i];
			z[m] = dot(v[m], v[m]);
			c[m] = c[m - 1] + e * v[m] / z[m] / 2;
			r[m] = r[m - 1] + e * e / z[m] / 4;
		}
		center = c[m];
		radius2 = r[m]; ++m;
	}
	void make_ball(list<point>::iterator i) {
		supp_end = ps.begin();
		if (m == dim + 1) return;
		for (list<point>::iterator k = ps.begin(); k != i; ) {
			list<point>::iterator j = k++;
			if (dist2(*j, center) > radius2) {
				push(*j); make_ball(j); pop();
				move_to_front(j);
			}
		}
	}
	void move_to_front(list<point>::iterator j) {
		if (supp_end == j) ++supp_end;
		ps.splice(ps.begin(), ps, j);
	}
};

int main() {
	
	int n;
	scanf("%d", &n);
	min_ball a;
	point p;
	int x, y;
	rep(i, n) {
		scanf("%d%d", &x, &y);
		p = { (double)x, (double)y };
		a.add(p);
	}
	a.compile();
	printdb(sqrt(a.radius2));

	Please AC;
}


Compiler output:
a.cc:177:9: error: 'list' does not name a type
  177 |         list<point> ps;
      |         ^~~~
a.cc:178:9: error: 'list' does not name a type
  178 |         list<point>::iterator supp_end;
      |         ^~~~
a.cc:200:24: error: 'list' has not been declared
  200 |         void make_ball(list<point>::iterator i) {
      |                        ^~~~
a.cc:200:28: error: expected ',' or '...' before '<' token
  200 |         void make_ball(list<point>::iterator i) {
      |                            ^
a.cc:211:28: error: 'list' has not been declared
  211 |         void move_to_front(list<point>::iterator j) {
      |                            ^~~~
a.cc:211:32: error: expected ',' or '...' before '<' token
  211 |         void move_to_front(list<point>::iterator j) {
      |                                ^
a.cc: In member function 'void min_ball::add(const point&)':
a.cc:158:17: error: 'ps' was not declared in this scope; did you mean 'p'?
  158 |                 ps.push_back(p);
      |                 ^~
      |                 p
a.cc: In member function 'void min_ball::compile()':
a.cc:164:27: error: 'ps' was not declared in this scope; did you mean 'pb'?
  164 |                 make_ball(ps.end());
      |                           ^~
      |                           pb
a.cc: In member function 'void min_ball::support(OUT)':
a.cc:168:22: error: 'ps' was not declared in this scope; did you mean 'pb'?
  168 |                 copy(ps.begin(), supp_end, out);
      |                      ^~
      |                      pb
a.cc:168:34: error: 'supp_end' was not declared in this scope
  168 |                 copy(ps.begin(), supp_end, out);
      |                                  ^~~~~~~~
a.cc: In member function 'void min_ball::make_ball(int)':
a.cc:201:17: error: 'supp_end' was not declared in this scope
  201 |                 supp_end = ps.begin();
      |                 ^~~~~~~~
a.cc:201:28: error: 'ps' was not declared in this scope; did you mean 'pb'?
  201 |                 supp_end = ps.begin();
      |                            ^~
      |                            pb
a.cc:203:22: error: 'list' was not declared in this scope
  203 |                 for (list<point>::iterator k = ps.begin(); k != i; ) {
      |                      ^~~~
a.cc:138:1: note: 'std::list' is defined in header '<list>'; this is probably fixable by adding '#include <list>'
  137 | #include <valarray>
  +++ |+#include <list>
  138 | 
a.cc:203:32: error: expected primary-expression before '>' token
  203 |                 for (list<point>::iterator k = ps.begin(); k != i; ) {
      |                                ^
a.cc:203:44: error: missing template arguments before 'k'
  203 |                 for (list<point>::iterator k = ps.begin(); k != i; ) {
      |                                            ^
a.cc:203:60: error: 'k' was not declared in this scope
  203 |                 for (list<point>::iterator k = ps.begin(); k != i; ) {
      |                                                            ^
a.cc:203:65: error: 'i' was not declared in this scope
  203 |                 for (list<point>::iterator k = ps.begin(); k != i; ) {
      |                                                                 ^
a.cc:204:35: error: expected primary-expression before '>' token
  204 |                         list<point>::iterator j = k++;
      |                                   ^
a.cc:204:47: error: missing template arguments before 'j'
  204 |                         list<point>::iterator j = k++;
      |                                               ^
a.cc:205:36: error: 'j' was not declared in this scope; did you mean 'jn'?
  205 |                         if (dist2(*j, center) > radius2) {
      |                                    ^
      |                                    jn
a.cc: In member function 'void min_ball::move_to_front(int)':
a.cc:212:21: error: 'supp_end' was not declared in this scope
  212 |                 if (supp_end == j) ++supp_end;
      |                     ^~~~~~~~
a.cc:212:33: error: 'j' was not declared in this scope; did you mean 'jn'?
  212 |                 if (supp_end == j) ++supp_end;
      |                                 ^
      |                                 jn
a.cc:213:17: error: 'ps' was not declared in this scope; did you mean 'pb'?
  213 |                 ps.splice(ps.begin(), ps, j);
      |                 ^~
      |                 pb
a.cc:213:43: error: 'j' was not declared in this scope; did you mean 'jn'?
  213 |                 ps.splice(ps.begin(), ps, j);
      |                                           ^
      |                                           jn