coord.cpp

struct coord {
    int i = 0;
    int j = 0;
};

// equality comparison between two coors
inline bool operator == (const coord &lhs, const coord &rhs) {
    return lhs.i == rhs.i && lhs.j == rhs.j;
}

// less then comparison between two coords
inline bool operator < (const coord &lhs, const coord &rhs) {
    return lhs.i < rhs.i || (lhs.i == rhs.i && lhs.j < rhs.j);
}