sort one array and other array following?

Question

here is the C++ sample

int a[1000] = {3,1,5,4}
int b[1000] = {7,9,11,3}

how do i make it so if i sort array a, array b also following array a

Answer 1

Generate an array the same size as the original, containing the indexes into the array: {0, 1, 2, 3}. Now use a custom comparator functor that compares the elements in an associated array rather than the indexes themselves.

template
class CompareIndices
{
public:
    CompareIndices(const T * array) : m_AssociatedArray(array) {}
    bool operator() (int left, int right) const
    {
        return std::less(m_AssociatedArray[left], m_AssociatedArray[right]);
    }
private:
    const T * m_AssociatedArray;
};

std::sort(i, i+4, CompareIndices(a));

Once you have a sorted list of indices, you can apply it to the original array a, or any other b array you want.