Go: package main

import (
	"fmt"
	"math"
)

func main() {
	var n int
	fmt.Scan(&n)
	for i := 0; i < n; i++ {
		var xa, ya, ra, xb, yb, rb float64
		fmt.Scan(&xa, &ya, &ra, &xb, &yb, &rb)
		// println(xa, ya, ra, xb, yb, rb)
		dis := math.Sqrt((xa-xb)*(xa-xb) + (ya-yb)*(ya-yb))
		if dis + ra < rb {
			fmt.Println(-2)
		} else if dis + rb < ra {
			fmt.Println(2)
		} else if dis > rb + ra {
			fmt.Println(0)
		} else {
			fmt.Println(1)
		}
	}
}

C++: #include <iostream>
#include <algorithm>
#include <cassert>
#include <cmath>
#include <stdio.h>
  
using namespace std;
  
//-------------------------------------------------------------------------
// geometric library
  
namespace geometry {
  
#define EPS 1E-10 ///< 0とみなすサイズ。適当
 
struct point {
    double x;
    double y;
 
    point& operator += (const point& rhs) { x += rhs.x; y += rhs.y; return *this; }
    point& operator -= (const point& rhs) { x -= rhs.x; y -= rhs.y; return *this; }
    point& operator /= (double factor) { x /= factor; y /= factor; return *this; }
    point& operator *= (double factor) { x *= factor; y *= factor; return *this; }
    bool operator == (const point& rhs) const { return (std::abs(x - rhs.x) < EPS) && (std::abs(y - rhs.y) < EPS); }
    bool operator != (const point& rhs) const { return !(*this == rhs); }
};
 
typedef point vector;
  
struct circle {
    point center;
    double radius;
};
  
struct line { // ax + by + c = 0
    double a;
    double b;
    double c;
};
 
enum rotate_dir {
    rotate_None = 0,
    rotate_CW   = 1,
    rotate_CCW  = -1
};
 
point operator + (const point& p1, const point& p2)
{
    point p(p1);
    p += p2;
    return p;
}
 
point operator / (const point& p1, double factor)
{
    point p(p1);
    p /= factor;
    return p;
}
  
point operator - (const point& p1, const point& p2)
{
    point p(p1);
    p -= p2;
    return p;
}
 
std::istream& operator >> (std::istream& is, point& p)
{
    is >> p.x >> p.y;
    return is;
}
 
///! 2点の距離
double get_distance(const point& p1, const point& p2)
{
    return sqrt(pow(p1.x - p2.x, 2) + pow(p1.y - p2.y, 2));
}
  
///! 2直線の交点
bool get_crosspoint(const line& l1, const line& l2, point *result)
{
    double denominator = l1.a * l2.b - l1.b * l2.a;
    if (std::abs(denominator) < EPS) {
        return false;
    }
    result->x = (l1.b * l2.c - l2.b * l1.c) / denominator;
    result->y = (l2.a * l1.c - l1.a * l2.c) / denominator;
    return true;
}
  
///! 2点の垂直2等分線
bool get_bisector(const point& p1, const point& p2, line *result)
{
    if (p1 == p2) {
        return false;
    }
    result->a = 2 * (p1.x - p2.x);
    result->b = 2 * (p1.y - p2.y);
    result->c = -(p1.y - p2.y) * (p1.y + p2.y) - (p1.x - p2.x) * (p1.x + p2.x);
    return true;
}

bool get_line(const point& p1, const point& p2, line *result)
{
    if (p1 == p2) {
        return false;
    }
    result->a = p2.y - p1.y;
    result->b = p1.x - p2.x;
    result->c = p1.y * p2.x - p1.x * p2.y;
    return true;
}
  
///! 外接円を求める
bool get_circum_circle(const point& p1, const point& p2, const point& p3, circle *result)
{
    double a = get_distance(p1, p2);
    double b = get_distance(p2, p3);
    double c = get_distance(p3, p1);
  
    // 半径の公式
    result->radius = a * b * c / sqrt((a + b + c) * (-a + b + c) * (a - b + c) * (a + b - c));
  
    line line_p1p2;
    line line_p2p3;
  
    // 頂点の垂直2等分線の交点が外心
    return get_bisector(p1, p2, &line_p1p2) &&
           get_bisector(p2, p3, &line_p2p3) &&
           get_crosspoint(line_p1p2, line_p2p3, &result->center);
}
 
double cross_product(const point& p1, const point& p2)
{
    return p1.x * p2.y - p2.x * p1.y;
}
 
///! p1-p2-p3が左右どちらの方向に折れているかを判定
rotate_dir direction(const point& p1, const point& p2, const point& p3)
{
    vector p1_p3 = p1 - p3;
    vector p2_p3 = p2 - p3;
    double cross = cross_product(p1_p3, p2_p3);
 
    if (std::abs(cross) < EPS) {
        return rotate_None;
    } else if (cross > 0) {
        return rotate_CW;
    } else {
        return rotate_CCW;
    }
}
  
// (p1s, p1e)と(p2s, p2e)の線分交差判定.EPS以下で接している場合はtrue、重なっている場合はfalse
bool intersect(const point& p1s, const point& p1e, const point& p2s, const point& p2e)
{
    assert(p1s != p1e && p2s != p2e);
    return
        (direction(p1s, p1e, p2s) != direction(p1s, p1e, p2e)) &&
        (direction(p2s, p2e, p1s) != direction(p2s, p2e, p1e));
}
 
// targetが三角形p1,p2,p3の内部にあるかどうか
bool is_inside_triangle(const point& p1, const point& p2, const point& p3, const point& target)
{
    point center_of_gravity = (p1 + p2 + p3) / 3; // 重心
 
    if (center_of_gravity == target) return true;
 
    // 重心とtargetを結んだ線分が三角形の辺と交叉するなら、点は三角形の外部にある
    bool intersect_any =
        intersect(p1, p2, center_of_gravity, target) ||
        intersect(p2, p3, center_of_gravity, target) ||
        intersect(p3, p1, center_of_gravity, target);
 
    return !intersect_any;
}

bool is_parallel(const point& p1, const point& p2, const point& p3, const point& p4)
{
    line l1, l2;
    point cross;

    if (!get_line(p1, p2, &l1) || !get_line(p3, p4, &l2)) {
        return false; // p1-p2, p3-p4で直線が作れない
    }
    return get_crosspoint(l1, l2, &cross) == false;
}
 
} // namespace geometry
  
//-------------------------------------------------------------------------
// solution
  
using namespace geometry;
 
int main(void)
{
    int n;
    cin >> n;

    for (int i = 0; i < n; i++) {
        circle cA, cB;
        cin >> cA.center >> cA.radius >> cB.center >> cB.radius;

        double distance = get_distance(cA.center, cB.center);

        if      (cB.radius + distance < cA.radius) { cout << "2";  }
        else if (cA.radius + distance < cB.radius) { cout << "-2"; }
        else if (cA.radius + cB.radius < distance) { cout << "0";  }
        else                                       { cout << "1";  }

        cout << endl;
    }

    return 0;
}

C++:  
 #include<iostream>
 #include<stdio.h>
 #include<string>
 #include<math.h>
 #include<iomanip>
 #include<algorithm>
 #include<string.h>
 #include<cctype>
 #include<map>
 #include<set>
 #include<vector>
 #include<sstream>
 #include<stack>
 
 using namespace std;
 
 double abs(double x)
 {
   if(x<0) return -x;
   else return x;       
 }
  
 int main()
 {
   int n;
   int result;
   cin>>n;
   double xa,ya,ra,xb,yb,rb;
   while(n--)
   {
     cin>>xa>>ya>>ra>>xb>>yb>>rb;
     double dis=sqrt(pow(yb-ya,2)+pow(xb-xa,2));
     if(dis>ra+rb) result=0;
     else if(dis>=abs(ra-rb)) result=1;
     else
     {
       if(dis+ra<rb) result=-2;
       else if(dis+rb<ra) result=2;    
     }
     cout<<result<<endl;        
   }
   //while(1);      
   return 0;    
 }

C++: #include<iostream>
#include<cmath>
using namespace std;
double a, b, c, d, e, f;
short int solve() {
	double dis = sqrt((a - d)*(a - d)+(b - e)*(b - e));
	if (dis > c + f)return 0;
	else if (dis < c - f)return 2;
	else if (dis < f - c)return -2;
	else return 1;
}
int main() {
	size_t n; cin >> n;
	for (size_t i = 0; i < n; i++){
		cin >> a >> b >> c >> d >> e >> f;
		cout << solve() << endl;
	}
}