Question

I have a vector < vector < Point> > X and want to copy all the elements in it into a vector < Point > Y (and in the same order if is possible)
I tried something like (in a for cycle):

Y.push_back(i) = X.at(i).at(i);

but obviously it doesn’t work…

I also find this (on stackoverflow) but it doesn’t work for me as well…

for (std::vector<std::vector<Point> >::iterator it = X.begin(), itEnd = X.end(); it != itEnd; ++it)
    Y.push_back((*it));

but the compiler tells me that “there isn’t an instance of function in overload” (and honestly I don’t even know what does it mean).

Answer 1

for(vector<vector<Point> >::iterator it = X.begin(); it != X.end(); ++it)
     Y.insert(Y.end(), it->begin(), it->end());

If you know the size of the resulting vector, you could call Y.reserve(finalYSize) before the loop.