Merge Sort STL Vectors

void MergeSort(vector<int> &vec)
{
    //if the vector has more than 1 element
    if(vec.size() > 1)
    {
        //separate the vector into two equal vectors
        vector<int> left(vec.begin(), vec.begin() + vec.size() / 2);
        vector<int> right(vec.begin() + vec.size() / 2, vec.end());

        //recursively call MergeSort for each part of the vector
        MergeSort(left);
        MergeSort(right);

        //make room for the new elements to be added
        vec.clear();

        //as long as both the left and the right vectors have elements
        //in them, put the smallest of each into vec one by one
        while (!left.empty() && !right.empty())
        {
            if(left[0] < right[0])
            {
                vec.push_back(left[0]);
                left.erase(left.begin());
            }
            else
            {
                vec.push_back(right[0]);
                right.erase(right.begin());
            }
        }

        //if there are no more elements in the left vector
        // put all those from the right vector directly into vec
        while(left.empty() && !right.empty())
        {
            vec.push_back(right[0]);
            right.erase(right.begin());
        }

        //the same when there are no more elements in the right vector
        while(!left.empty() && right.empty())
        {
            vec.push_back(left[0]);
            left.erase(left.begin());
        }

    }

}