remove duplicates from comma separated string

Question

Is there a better (faster) solution to remove duplicates from a comma separated string?

public function d($dep) { 
    if (strpos($dep,\',\') !== false) {
           


        

Answer 1

You could use the uniqueness of array keys:

function d($dep) {
    return implode(',', array_keys(array_flip(explode(',', $dep))));
}

array_flip swaps the key-value association, so the values become the keys and vice versa. This will automatically eliminate duplicates. Its runtime complexity is O(n).

Answer 2

Many many thanks guys. Finally, we have two solutions (Pascal and Ericso gave the same solution) here and the question became which one is faster. To be honest, by faster, I meant what executes faster and if I take words of Gumbo, I get the combined functions of array_keys and array_flip is faster than array_unique. Because, the two other functions, implode and explode are same.

return implode(',', array_unique(explode(',', $dep)));
return implode(',', array_keys(array_flip(explode(',', $dep))));

Finally I gave 1 up to all three ad many thanks that can't be measured / seen. I agree that either of the three solutions can be expected, but then took the answer of Gumbo believing that array_keys(array_flip()) is faster to execute than array_unique() in the given context.

Cheers.

Answer 3

$str = implode(',',array_unique(explode(',', $str)));

Answer 4

I would probably use the same kind of idea that what you posted ; but I think you can remove your two conditions, to use only this :

$exploded = explode(',', $str);
$unique = array_unique($exploded);
$imploded = implode(',', $unique);
var_dump($imploded);

I've tested it with those three strings, and it seems to work in each case :

$str = 'a,b,c,d,a,c,e,f';
$str = 'a,a';
$str = 'a';

Notes :

• Using explode on a string that doesn't contain the delimiter will return an array with one element -- your test with strpos is not necessary.
• And using implode on an array with only one element will work too (not adding any delimiter) -- your test with the ternary operator is not necessary either.

Of course, you can also remove the variables, and use only one line :

$result = implode(',', array_unique(explode(',', $str)));

Not sure it's easier to understand that way, though...

Answer 5

Try just this:

$uniqueDep = implode(',', array_unique(explode(',', $dep)));