Problem 391. Poker Series 11: selectBestHand

Created by Doug Hull
Appears in Card Games

Difficulty:Rate

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The Poker Series consists of many short, well defined functions that when combined will lead to complex behavior. Our goal is to create a function that will take two hand matrices (defined below) and return the winning hand.

A hand matrix is 4x13 binary matrix showing the cards that are available for a poker player to use. This program will be expandable to use 5 card hands through 52 card hands! Suits of the cards are all equally ranked, so they only matter for determination of flushes (and straight flushes).

For each challenge, you should feel free to reuse your solutions from prior challenges in the series. To break this problem into smaller pieces, I am likely making architectural choices that are sub-optimal for speed. This is being done as an exercise in coding. The larger goal of this project can likely be done in a much faster, but more obscure way.

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Select the best hand using the definitions from earlier in this series.

out.hm{1} = cards used from the first hand matrix;
out.hm{2} = cards used from the second hand matrix;   
out.winner = 1,2 or zero for a tie;

Standard poker ranks apply: Straight flush is best, high card is worst, with many gradations within each rank.

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193 Solutions
35 Solvers

Last Solution submitted on Dec 13, 2024

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15 Comments

15 Comments

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@bmtran (Bryant Tran) on 23 Feb 2012

that took a really long time to do...

i think that it might be beneficial to return more information in the subfunctions such as the kicker(s) and the values of the cards themselves.

Alfonso Nieto-Castanon on 24 Feb 2012

It's not that hard, using a modified hand card representation (sorting columns as A,K...2 and adding a repeated A for the straights) makes the comparison of two hands trivially simple (sortrows)

Alfonso Nieto-Castanon on 24 Feb 2012

What i believe might have been beneficial would be to have the hand cards columns sorted by decreasing card value -like its rows- since all computations look much cleaner that way ...

Alfonso Nieto-Castanon on 25 Feb 2012

scratch the above, it does need more work (and we need more test samples)

Alfonso Nieto-Castanon on 28 Feb 2012

When deciding the best hand among two hands of the same rank (e.g. both players have a pair of 5's) what is more important, the suits of the hand or the rank of the kicker(s)? (i guess the latter but the test suite does not discriminate)

Alfonso Nieto-Castanon on 28 Feb 2012

perhaps you could add these tests (most of the current solvers fail one or the other): TEST1: hm1=[ 0 0 0 0 0 0 0 0 0 1 0 1 0; 0 0 0 0 0 0 0 0 0 0 0 1 0; 0 0 0 0 0 0 0 0 0 1 0 0 0; 0 0 0 0 0 0 0 0 0 0 0 1 0];
hm2=[ 0 0 0 0 0 0 0 0 0 0 0 0 0; 1 0 0 0 0 0 0 0 0 0 0 1 0; 1 0 0 0 0 0 0 0 0 0 0 1 0; 0 0 0 0 0 0 0 0 0 0 0 1 0];
out.hm{1} = hm1;
out.hm{2} = hm2;
out.winner = 2;
TEST2: hm1=[ 0 0 0 1 1 1 1 1 0 0 0 0 0; 0 0 0 0 0 0 0 0 0 0 0 0 0; 0 0 0 0 0 0 0 0 0 0 0 0 0; 0 0 0 0 0 0 0 0 0 0 0 0 0];
hm2=[ 0 0 0 0 0 0 0 0 0 0 0 0 0; 0 0 0 1 1 1 1 1 0 0 0 0 0; 0 0 0 0 0 0 0 0 0 0 0 0 0; 0 0 0 0 0 0 0 0 0 0 0 0 0];
out.hm{1} = hm1;
out.hm{2} = hm2;
out.winner = 0;

Albert Yam on 29 Feb 2012

hm1=[1 0 0 0 0 0 0 0 0 0 0 0 1;1 0 0 0 0 0 0 0 0 0 0 0 0;1 0 0 0 0 0 0 0 0 0 0 0 0;1 0 0 0 0 0 0 0 0 0 0 0 0];
hm2=[1 0 0 0 0 0 0 0 0 0 0 0 0;1 0 0 0 0 0 0 0 0 0 0 0 0;1 0 0 0 0 0 0 0 0 0 0 0 0;1 0 0 0 0 0 0 0 0 0 0 0 1];
Is player 1 supposed to win in this case?

Albert Yam on 29 Feb 2012

On a second thought.. shouldn't there be only one deck?

Alfonso Nieto-Castanon on 1 Mar 2012

@albert: your example should be a tie (the card suits do not break ties; in fact they are not used at all for scoring). And I believe there is no limitation on the number of decks the hand cards come from...

Andrew Dobrovolc on 14 Jun 2017

Test case 7 is broken, the case is expecting matrices of type double in the output, but all other cases want matrices of type logical.

Athi on 9 Dec 2018

Test case 7 is confusing.

hm2 = [1 1 1 1 1 1 0 0 0 0 0 1 1
0 0 0 0 0 0 0 0 0 0 0 1 0
0 0 0 0 0 0 1 0 0 0 0 0 0
0 0 0 0 1 0 0 0 0 0 0 0 0];

om2 = [0 1 1 1 1 1 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0];

1. Why the StraightFlush including Ace is not considered as the BestHand for hm2?
2. How could the winner be 2, since the first player has Ace in its BestHand?

HighPhi on 26 Jul 2020

Seconding both Athi's & Andrew's posts

Player 2 has an ace in his hand but chooses to play 2 3 4 5 6
That's backwards

also, the double thing is 100% true. why switch from logical to double

Rafael S.T. Vieira on 13 Sep 2020

Many of the issues could have been easily solved with a better design choice (for instance, cases 5 and 9 are only an issue because the functions that identify both hands do not store the highest cards values). Storing the array usedCards is not useful, it would be best to store a number representing the hand, and the values of the highest cards or a number representing them.

Richard Ferrara on 1 Feb 2021

For those asking why 2-3-4-5-6 beats A-2-3-4-5: in poker, the rank of a straight is determined by the card at the high end. So 2-3-4-5-6 beats A-2-3-4-5 because 6 beats 5. The ace becomes a low card.

Augusto Mazzei on 28 Feb 2022

smartest non-cheating solution is scored 480? omegaLOL

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