c++ - std::map with cv::Point as key -

c++ - std::map with cv::Point as key -

i need create std::map<cv::point, double>. cv::point type of point opencv library. has fields like: x , y.

cv::point not have < operator of course. have thought how define have optimal access element in std::map?

in other words. have illustration 20000 points. need quite fast access every point.

for example:

std::map<cv::point, double> mymap; point p(10, 234); int value = 777; mymap[p] = value; // need operation quite fast decided utilize std::map

but cv::point not have < operator. can prepare < operator (it comparing illustration x coordinate):

bool operator<(const cv::point a, const cv::point b) { homecoming a.x < a.x; }

but guess not operator. many points has same value of x.

how prepare efficient operator in case?

according this documentation, cv::point represents 2 dimensional datapoint. this, can define operator < via standard lexicographic ordering:

bool operator<(cv::point const& a, cv::point const& b) { homecoming (a.x < b.x) || (a.x == b.x && a.y < b.y); }

edit: considered using unordered_map: although might more appropriate here, bit more complicated implement have combine 2 hash-values of x , y. can utilize boost::hash_combine or figure out reasonable on own, see becomes more complicated.

c++ algorithm opencv data-structures stl