Makefile

randcoll: randcoll.cpp
	g++ -g randcoll.cpp -std=c++11 -o randcoll

randcoll.cpp

/*
 * This small exercise aims to propose an implementation of the main
 * collision checking loop of a fictional 3D game engine.
 *
 * Our game engine supports two types of objects: Cubes and Spheres.
 * We are trying to come up with the most elegant (ie easy to
 * understand and maintain) solution for choosing among three possible
 * collision check cases: Cube <=> Cube, Sphere <=> Sphere, and
 * Cube <=> Sphere.
 *
 * Please fork this gist and submit a path with the following TODO items
 * completed.
 *
 * TODO Items:
 *   1. Fix std::vector definition for the object array named "objects"
 *   2. Add 2 cubes and 2 spheres to the objects array.
 *   3. Implement collides_with member methods for all object types.
 *      ie. cube <=> cube, cube <=> sphere and sphere <=> sphere
 *      The functions themselves are to be EMPTY!. no actual collision
 *      detection code is requested. Just make them return true or false
 *      randomly!
 */


#include <time.h>
#include <vector>
#include <random>
#include <iostream>
#include <typeinfo>


bool true_or_false() {
    return std::rand() % 2;
}


class Object;
class Sphere;
class Cube;

class Object {
public:
    explicit Object()
            : m_object_id(++s_num_objects) {

    }

    int get_object_id() const {
        return m_object_id;
    }

    static int get_num_objects() {
        return s_num_objects;
    }

    bool operator==(const Object &other) const {
        return m_object_id == other.get_object_id();
    }

    virtual bool collides_with(Object &obj) = 0;
    /* TODO 3 */

private:
    static int s_num_objects;
    int m_object_id;
};


class Sphere: public Object {
    /* TODO 3 */
};

class Cube: public Object {
    /* TODO 3 */
};

std::vector<Object> objects; // FIXME 1: Fix the object type here.


int main(void) {
    srand(time(NULL));

    /* TODO 2: add two spheres and two cubes to the objects array */

    for(int i = 0; i < objects.size(); ++i) {
        auto &obj1 = objects.at(i);
        for(int j = i; j < objects.size(); ++j) {
            auto &obj2 = objects.at(j);
            if (obj1 == obj2) {
                continue;
            }

            /* TODO 3: implement collides_with */
            if (obj1.collides_with(obj2)) {
                /* as an example
                std::cout
                    << "object id " << obj1.get_object_id()
                    << " of type " << typeid(obj1).name()
                    << " collides with "
                    << "object id " << obj2.get_object_id()
                    << " of type " << typeid(obj2).name();
                */
            }
            else {
                /* as an example
                std::cout
                    << "object id " << obj1.get_object_id()
                    << " of type " << typeid(obj1).name()
                    << " does NOT collide with "
                    << "object id " << obj2.get_object_id()
                    << " of type " << typeid(obj2).name();
                */
            }
        }
    }

    return 0;
}

sample.out

object id 1 of type 4Cube check Cube => Cube  collides with object id 2 of type 4Cube
object id 1 of type 4Cube check Sphere => Cube  collides with object id 3 of type 6Sphere
object id 1 of type 4Cube check Sphere => Cube  does not collide with object id 4 of type 6Sphere
object id 2 of type 4Cube check Sphere => Cube  collides with object id 3 of type 6Sphere
object id 2 of type 4Cube check Sphere => Cube  does not collide with object id 4 of type 6Sphere
object id 3 of type 6Sphere check Sphere => Sphere  collides with object id 4 of type 6Sphere