C++, copy set to vector

Solution 1:

You need to use a back_inserter:

std::copy(input.begin(), input.end(), std::back_inserter(output));

std::copy doesn't add elements to the container into which you are inserting: it can't; it only has an iterator into the container. Because of this, if you pass an output iterator directly to std::copy, you must make sure it points to a range that is at least large enough to hold the input range.

std::back_inserter creates an output iterator that calls push_back on a container for each element, so each element is inserted into the container. Alternatively, you could have created a sufficient number of elements in the std::vector to hold the range being copied:

std::vector<double> output(input.size());
std::copy(input.begin(), input.end(), output.begin());

Or, you could use the std::vector range constructor:

std::vector<double> output(input.begin(), input.end()); 

Solution 2:

Just use the constructor for the vector that takes iterators:

std::set<T> s;

//...

std::vector v( s.begin(), s.end() );

Assumes you just want the content of s in v, and there's nothing in v prior to copying the data to it.

Solution 3:

here's another alternative using vector::assign:

theVector.assign(theSet.begin(), theSet.end());