C++ Solution:

vector missingNumbers(vector arr, vector brr) {

std::vector<int> vecMissingNumbers;
std::array<int, 101> arrFrequency{0};

//Find minimum element in brr
int minBrr = *std::min_element(brr.begin(), brr.end());

cout << "Min = " << minBrr;

//Store frequency in an array with index relative to the smallest number in brr
for(int number: brr)
{
    int index = number - minBrr;
    cout << index << " ";
    arrFrequency.at(index)++;
}

//Subtract count from frequency array based on arr
for(int number: arr)
{
    int index = number - minBrr;
    cout << index << " ";
    arrFrequency.at(index)--;
}

//Check non-zero frequency and store in vector
for(int index = 0; index < 100; index++)
{
    if(arrFrequency.at(index) != 0)
    {
        vecMissingNumbers.push_back(index+minBrr);
    }
}

return vecMissingNumbers;

}