Check for poker straight

I have managed to create an algorithm to check the rank of a poker hand. It works 100% correctly, but it's very slow. I've been analysing the code, and the check straight function is one of the slowest parts of it.

So my question is, is there a better way of calculating whether a hand make a straight?

Here is some details:

7 cards, 2 from holder, 5 from board. A can be high or low.

Each card is assigned a value: 2 = 2 3 = 3 .. 9 = 9 T = 10 J = 11 Q = 12 K = 13 A = 14

The script has an array of all 7 cards:

$cards = array(12,5,6,7,4,11,3);

So now I need to be able to sort this into an array where it:

discards duplicates
orders the card from lowest to highest
only returns 5 consecutive cards I.e. (3,4,5,6,7)

It needs to be fast; loops and iterations are very costly. This is what I currently use and when it tries to analyse say 15000 hands, it takes its toll on the script.

For the above, I used:

discard duplicates (use array_unique)
order cards from lowest to highest (use sort())
only return 5 consecutive cards (use a for loop to check the values of cards)

Does anyone have any examples of how I could improve on this? Maybe even in another language that I could perhaps look at and see how it's done?

Solution

Instead of working with array deduping and sorting, consider using a bitmask instead, and setting bits to 1 where the card value is set. A bitmask works like a Set datastructure and comes with additional advantages when it comes to detecting contiguous elements.

for ($i = 0; $i < count($cards); $i++) {
    $card = $cards[$i];
    // For each card value, set the bit
    if ($card == 14) {
        // If card is an ace, also set bit 1 for wheel
        $cardBitmask |= 0x2;
    }
    $cardBitmask |= (1 << $card);
}

// To compare, you simply write a for loop checking for 5 consecutive bits
for($i = 10; $i > 0; $i--)
{
    if ($cardBitmask & (0x1F << $i) == (0x1F << $i)) {
        // Straight $i high was found!
    }
}