Question

I have two methods like this

HashSet<Tuple<int,int>> _xyPairs = new HashSet<Tuple<int,int>>();
private void SetTravelled(int x, int y, bool travelled)
{
    var t = new Tuple<int, int>(x, y);

    if (travelled)
        _xyPairs.Add(t);
    else
        _xyPairs.Remove(t);
}

private bool HaveTravelled(int x, int y)
{
    return _xyPairs.Contains(new Tuple<int, int>(x, y));
}

I don’t mind the first method so much because it’s not called very often. The second method however is called very frequently. So I have to create new Tuple’s over and over.

Is there a way to combine the two integers into one value for the Hashset?

Answer 1

If you have an indication that the tuple is actually causing you a problem, you could try to combine the two 32-bit integers into one 64-bit integer:

HashSet<long> _xyPairs = new HashSet<long>();

private void SetTravelled(int x, int y, bool travelled)
{
    var t = Combine(x, y)
    ...

private bool HaveTravelled(int x, int y)
{
    return _xyPairs.Contains(Combine(x, y));
}

private static long Combine(int x, int y)
{
    return (long)(((ulong)x) | ((ulong)y) << 32);
}