Array symmetric difference X23420

Write a function that returns a sorted vector with the symmetric difference of two sorted vectors $v_1$ and $v_2$. The result must have the elements in $v_1$ that are not in $v_2$ and the elements in $v_2$ that are not in $v_1$, without repetitions. For example, the symmetric difference of a vector with $1, 2, 2, 5, 5, 7$ and a vector with $2, 3, 3, 7$ is a vector with $1, 3, 5$.

Interface

vector<double> symmetric_difference(const vector<double>& v1, const vector<double>& v2);

Observation

You only need to submit the required procedure; your main program will be ignored.