Swap rows in a 2D array with std::swap. How does it work?

Question

I'm mostly just documenting this question as someone may stumble upon it, and may find it useful. And also, I'm very curios with, how does std::swap works on a 2D array like: Arr[10][10] .

My question arised because as to my understanding an array like this is just a 1D array with some reindexing.
For reference: How are 2-Dimensional Arrays stored in memory?

int main()
{
    const int x = 10;
    const int y = 10;
    int Arr[y][x];
    // fill the array with some elements...
    for (int i = 0; i < x*y; i++)
    {
        Arr[i / y][i % x] = i;
    }

    // swap 'row 5 & 2'
    // ??? how does swap know how many elements to swap?
    // if it is in fact stored in a 1D array, just the
    // compiler will reindex it for us
    std::swap(Arr[5], Arr[2]);

    return 0;
}

I could understand swapping two 'rows' if our data type is, say a pointer to a pointer like int** Arr2D then swap with std::swap(Arr2D[2], Arr2D[5]) as we do not need to know the length here, we just need to swap the two pointers, pointing to '1D arrays'.
But how does std::swap work with Arr[y][x] ?
Is it using a loop maybe, to swap all elements within x length?

Answer 1

std::swap has an overload for arrays that effectively swaps each two elements, again, using std::swap .

As for the size information, it is embedded within the array type ( Arr[i] is int[x] ), so the compiler knows to deduce T2 as int and N as 10 .

OT: Why aren't variable-length arrays part of the C++ standard? ( but this particular case is OK )