How would I refactor this to use iterator or otherwise not construct and return a container?

[hollow dome]

std::vector<uint16_t> NeighborsOfCell(int cellX, int cellY)
{
    std::vector<uint16_t> neighbors;
    if (cellX > 0 && cellY > 0) [[likely]] {
        const auto &cell = m_cells[(cellX - 1) + NUM_CELLS * (cellY - 1)];
        neighbors.insert(neighbors.end(), cell.begin(), cell.end());
    }
    if (cellX > 0) [[likely]] {
        const auto &cell = m_cells[(cellX - 1) + NUM_CELLS * cellY];
        neighbors.insert(neighbors.end(), cell.begin(), cell.end());
    }
    if (cellY > 0) [[likely]] {
        const auto &cell = m_cells[cellX + NUM_CELLS * (cellY - 1)];
        neighbors.insert(neighbors.end(), cell.begin(), cell.end());
    }
    if (cellX > 0 && cellY < NUM_CELLS - 1) [[likely]] {
        const auto &cell = m_cells[(cellX - 1) + NUM_CELLS * (cellY + 1)];
        neighbors.insert(neighbors.end(), cell.begin(), cell.end());
    }
    return neighbors;
}

This is only a performance issue in debug builds. If I were to use an iterator instead is there a way to effectively "concatenate" the iterators begin and end to cover the same neighbors?

I think that I want to return a std::vector<uint16_t>::iterator?

[mortal cosmos]

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[hollow dome]

apparently there is a way to make it work with joining views or something but it runs even worse

!solved

[mortal cosmos]

Thank you and let us know if you have any more questions!

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[static jacinth]

A simple solution is to not return anything

Instead accept a function and call it for each neighbor