Language: C++

#include<iostream>
using namespace std;
int main(){
	int n;
	double x[3], y[3], a, b, c, d, e, f, l , m, n;
	cin >> n;
	while(n--){
????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
		
		a = 2 * (x[1] - x[0]);
		b = 2 * (y[1] - y[0]);
		c = ( (x[1]*x[1]) + (y[1]*y[1]) ) -( (x[0]*x[0]) + (y[0]*y[0]) );
		
		d = 2 * (x[2] - x[0]);
		e = 2 * (y[2] - y[0]);
		f = ( (x[2]*x[2]) + (y[2]*y[2]) ) -( (x[0]*x[0]) + (y[0]*y[0]) );
		
		l = (c*e - f*b) / (a*e - d*b);
		m = (c*d - f*a) / (b*d - e*a);
		
		n = sqrt((l - x[0])*(l - x[0]) + (m - y[0])*(m - y[0]));
		
		cout << fixed << setprecision(3) << l << " " << m << " " << n << endl;
	}
}

Compiler output:
a.cc: In function 'int main()':
a.cc:5:53: error: conflicting declaration 'double n'
    5 |         double x[3], y[3], a, b, c, d, e, f, l , m, n;
      |                                                     ^
a.cc:4:13: note: previous declaration as 'int n'
    4 |         int n;
      |             ^
a.cc:8:1: error: expected primary-expression before '?' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      | ^
a.cc:8:2: error: expected primary-expression before '?' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |  ^
a.cc:8:3: error: expected primary-expression before '?' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |   ^
a.cc:8:4: error: expected primary-expression before '?' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |    ^
a.cc:8:5: error: expected primary-expression before '?' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |     ^
a.cc:8:6: error: expected primary-expression before '?' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |      ^
a.cc:8:7: error: expected primary-expression before '?' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |       ^
a.cc:8:8: error: expected primary-expression before '?' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |        ^
a.cc:8:9: error: expected primary-expression before '?' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |         ^
a.cc:8:10: error: expected primary-expression before '?' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |          ^
a.cc:8:11: error: expected primary-expression before '?' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |           ^
a.cc:8:12: error: expected primary-expression before '?' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |            ^
a.cc:8:13: error: expected primary-expression before '?' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |             ^
a.cc:8:14: error: expected primary-expression before '?' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |              ^
a.cc:8:15: error: expected primary-expression before '?' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |               ^
a.cc:8:16: error: expected primary-expression before '?' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |                ^
a.cc:8:67: error: expected ':' before ';' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |                                                                   ^
      |                                                                   :
a.cc:8:67: error: expected primary-expression before ';' token
a.cc:8:67: error: expected ':' before ';' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |                                                                   ^
      |                                                                   :
a.cc:8:67: error: expected primary-expression before ';' token
a.cc:8:67: error: expected ':' before ';' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |                                                                   ^
      |                                                                   :
a.cc:8:67: error: expected primary-expression before ';' token
a.cc:8:67: error: expected ':' before ';' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |                                                                   ^
      |                                                                   :
a.cc:8:67: error: expected primary-expression before ';' token
a.cc:8:67: error: expected ':' before ';' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |                                                                   ^
      |                                                                   :
a.cc:8:67: error: expected primary-expression before ';' token
a.cc:8:67: error: expected ':' before ';' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |                                                                   ^
      |                                                                   :
a.cc:8:67: error: expected primary-expression before ';' token
a.cc:8:67: error: expected ':' before ';' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |                                                                   ^
      |                                                                   :
a.cc:8:67: error: expected primary-expression before ';' token
a.cc:8:67: error: expected ':' before ';' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |                                                                   ^
      |                                                                   :
a.cc:8:67: error: expected primary-expression before ';' token
a.cc:8:67: error: expected ':' before ';' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |                                                                   ^
      |                                                                   :
a.cc:8:67: error: expected primary-expression before ';' token
a.cc:8:67: error: expected ':' before ';' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |                                                                   ^
      |                                                                   :
a.cc:8:67: error: expected primary-expression before ';' token
a.cc:8:67: error: expected ':' before ';' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |                                                                   ^
      |                                                                   :
a.cc:8:67: error: expected primary-expression before ';' token
a.cc:8:67: error: expected ':' before ';' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |                                                                   ^
      |                                                                   :
a.cc:8:67: error: expected primary-expression before ';' token
a.cc:8:67: error: expected ':' before ';' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |                                                                   ^
      |                                                                   :
a.cc:8:67: error: expected primary-expression before ';' token
a.cc:8:67: error: expected ':' before ';' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |                                                                   ^
      |                                                                   :
a.cc:8:67: error: expected primary-expression before ';' token
a.cc:8:67: error: expected ':' before ';' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |                                                                   ^
      |                                                                   :
a.cc:8:67: error: expected primary-expression before ';' token
a.cc:8:67: error: expected ':' before ';' token
    8 | ????????????????cin>> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
      |                                                                   ^
      |                                                                   :
a.cc:8:67: error: expected primary-expression before ';' token
a.cc:21:21: error: 'sqrt' was not declared in this scope
   21 |                 n = sqrt((l - x[0])*(l - x[0]) + (m - y[0])*(m - y[0]));
      |                     ^~~~
a.cc:23:34: error: 'setprecision' was not declared in this scope
   23 |                 cout << fixed << setprecision(3) << l << " " << m << " " << n << endl;
      |                                  ^~~~~~~~~~~~
a.cc:2:1: note: 'std::setprecision' is defined in header '<iomanip>'; this is probably fixable by adding '#include <iomanip>'
    1 | #include<iostream>
  +++ |+#include <iomanip>
    2 | using namespace std;