public Pfs Add(int n)
{
var builder = Values.ToBuilder();
if (builder.TryGetValue(n, out int val))
{
val++;
}
else
{
val = 1;
}
builder[n] = val;
var pfs = new Pfs(builder.ToImmutable());
return(pfs);
}
public static Pfs operator +(Pfs lhs, Pfs rhs)
{
var tot = lhs.Values.Keys.Concat(rhs.Values.Keys).Distinct()
.Select(k =>
{
if (!lhs.Values.TryGetValue(k, out int val))
{
val = 0;
}
if (rhs.Values.TryGetValue(k, out int rval))
{
val += rval;
}
return(new KeyValuePair <int, int>(k, val));
}).ToImmutableDictionary();
var result = new Pfs(tot, lhs.Total * rhs.Total);
return(result);
}