> Do you have a dynamic programming solution which runs reasonably fast
> in another language? Because this game of kyles looks like an example
> from combinatoric game theory to me and as such it might be much more
> efficient to solve it using nim-sums (if possible; I haven't given this
> too much thought).
> 
> Also note that, since your strings only consist of X and I, you could
> also use Integers and bit-operations instead of lists in your
> algorithms. You'd still need a Map for memoization, but other operations
> might be much faster.
> 
> Cheers