how to organize or sort a std::vector

Question

I have a vector full of cv::Point and I want to organize this vector so, that the Point with the smallest x and y value should be the first and the last one should have the

Answer 1

Use std::sort.

std::sort(vec.begin(), vec.end(), [](const cv::Point2f &a, const cv::Point2f &b) {
    return (/* This is where you would compare a and b however you want */);
});

Really, it's quite hard to tell what you deem as the greatest (x,y) pair and the least (x,y) pair. One solution is to add the coordinates to give them a magnitude.

I'd use the distance from the origin: return a.x*a.x + a.y*a.y < b.x*b.x + b.y*b.y

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In case you can't use C++11 functionality, here's the equivalent of the above solution:

bool point_comparator(const cv::Point2f &a, const cv::Point2f &b) {
    return (/* Your expression */);
}

std::sort(vec.begin(), vec.end(), point_comparator);