Poker hand flop evaluator

Question

I want to create a lookup table for texas hold'em poker hands. Right now, I am using prime numbers to represent each card, and want to figure out what those cards represent as a total hand. This is because the order of the cards don't matter and the multiplication will provide us with a unique number. Now, I know about the hand evaluators, but they only evaluate the strength of the hand without draws, and do not separate the hands into as many categories as I need.

As an example take the following situation: Hand: AdKd Flop: Kc5d3d

(d = diamonds, c = clubs, h = hearts, s = spades) Now, this would return from the lookup table a pair and also a flush draw.

Now this is more tricky: Hand: AhAd Flop: 5c5h3d

This would evaluate to overpair. So, basically, we cannot combine the hand and the flop into a single number, as we want to know exactly how the hand interacts with the flop.

I have already created a way of determining if a flush or a flush draw exists and whether a straight or a straight draw exists. So after that, the suits no longer matter, and we don't care about non-pair hands. Basically, given two numbers that represent the hand and the flop, we get back a hand category. For the last example, Aces are the prime number 41, so for the hand we get 41*41=1681 and for the board, we get 7*7*3=147. Ok now, we go to our lookup table and enter this lookup(147, 1681) and it should return OVERPAIR (or whatever constant we set it to), in constant time.

How do I implement first the lookup table? And the lookup function? (I'm already planning on using a perfect hashing algorithm for both the flop and the hand, but don't really know how to combine them.)

Answer 1

First, for encoding hands I find your approach very raw (not sure why you would use 41 for Ace, why not 37, and how do you differentiate different flavors of Aces). I would suggest the following.

For hand use a number between 1 and 52*51/2 to denote every combination. For flop use 52*51*50/(2*3) numbers and 52*51*50*49/(2*3*4) for flop+turn.

Each combination of these numbers will denote each unique situation. So store whatever annotation (straight, straight-flop etc) you want for each of these.