[RESOLVED] remove values in $b[] from $a[] without using functions

jrough

I am not sure about this assignment line $temp[$i. ','.$key] = $temp[$i]; ?
I think it is supposed to reset the index?
I can't use array_unique, array_diff or array_find or array_filter functions because the problem is to remove what is in strB from strA, including dupes, but leave the duplicates and every string that isn't in A. I can't use array_unique to remove the duplicates first and I can't compare the two arrays with array_diff because it won't work with dupes and if I use array_find to find the values in A from B it will only find the first one, correct me if I'm wrong.
I got this test line from the php manual but I don't understand why the searched for value and the $key value is set to equal the temp[$i] before it is unset but all I need to do is remove all the values in $bStr in $aStr. In any case I am getting a syntax error. With the reference to $aStr that variable should have the value of the removed strings but now I have a syntax error.
thanks,


$aStr= array('a','a','b','b','c','d','d','e');
$bStr= array('b','c','d','d','f');
$aInt= array(1,1,2,2,3,3,4,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,18,19);
$bInt= array(1,3,5,7,9,11,13,15,15,17,17,19,19,20,20,21,22,23,24);

echo "<pre>"; 
print_r($aStr);
echo "</pre>";


echo "<pre>";
print_r($bStr);
echo "</pre>";

function new_array($b,&$a){
$temp= array();
foreach ($b as $key=>$val){
	$i = array_search($val, $a);

if(!empty($i) ){
	$temp[$i. ','.$key] = $temp[$i];
	unset($temp[$i]);
}
}

$new=new_array($bStr,$aStr));

echo "<pre>";
print_r($aStr);
echo "</pre>";

thanks,

laserlight

jrough wrote:
the problem is to remove what is in strB from strA, including dupes, but leave the duplicates and every string that isn't in A

Instead of talking so much about what you cannot do, start by talking about what you are trying to do.

So, you want to remove every string in the first array that matches a string from the second array. Nothing else from the first array should be removed. Let's see:

Must order be maintained?
If 'a' appears twice in the first array and only once in the second array, should both instances of 'a' be removed from the first array or should only the first instance of 'a' in the first array be removed?

jrough

yes, both instances of "a" should be removed but only if it is in "b". I don't think the order is important but I have to do this on numbers also..

laserlight

jrough wrote:
yes, both instances of "a" should be removed but only if it is in "b".

In that case array_diff will suffice, contrary to your claim that it would not. If you want to re-number the keys, use array_walk on the return value of array_diff.

jrough wrote:
I don't think the order is important but I have to do this on numbers also..

I asked about order because sorting may help if an algorithm had to be implemented by hand.

EDIT:
By the way, please be accurate and precise when stating your requirements. For example, your statement that 'both instances of "a" should be removed but only if it is in "b"' is actually nonsensical because "b" does not contain any instances of "a" since "b" is a string.

bradgrafelman

laserlight;10985411 wrote:
In that case array_diff will suffice, contrary to your claim that it would not.

I'm guessing that his claim that it "would not [suffice]" is mostly due to the fact that his homework assignment says not to use it. 😉

EDIT: Hmm.. looks like I was reading into "assignment line" in the wrong way. I'm still a bit confused as to what the intent is based on the original code, though, so perhaps I'm just a bit too confused on multiple points.

jrough

okay, thanks I see your point I will try it with array_diff but just for learning purposes what is wrong with the below?
This would work if you wanted to leave one of the duplicates in $aStr found in $bStr. thanks,

 
$aStr= array('a','a','b','b','c','d','d','e');
$bStr= array('b','c','d','d','f');
$aInt= array(1,1,2,2,3,3,4,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,18,19);
$bInt= array(1,3,5,7,9,11,13,15,15,17,17,19,19,20,20,21,22,23,24);

echo "<pre>"; 
print_r($aStr);
echo "</pre>";


echo "<pre>";
print_r($bStr);
echo "</pre>";

function new_array($b,$a){

foreach ($b as $key=>$val){
	$i = array_search($val, $a);

if(!empty($i) ){

	unset($a[$i]);
	echo $i; ."---------------<br />"
}
}

$new=new_array($bStr,&$aStr));

echo "<pre>";
print_r($aStr);
echo "</pre>";

laserlight

bradgrafelman wrote:
I'm still a bit confused as to what the intent is based on the original code, though, so perhaps I'm just a bit too confused on multiple points.

Of course, we know that not all code submitted as comments to the PHP manual is good 😉
At a glance, the use of empty is wrong since 0 is a valid index. $temp[$i] might not even exist... maybe it was supposed to be empty($temp[$i]) or something, but frankly I don't think we need to bother with it any further.

laserlight

jrough wrote:
just for learning purposes what is wrong with the below?
This would work if you wanted to leave one of the duplicates in $aStr found in $bStr.

I mentioned some of what was wrong from my previous post since your new example is based on that. If you want to keep duplicates, something like this should work:

function array_diff_keep_dup($array1, $array2) {
    foreach ($array2 as $value) {
        $key = array_search($value, $array1);
        if ($key !== false) {
            unset($array1[$key]);
        }
    }
    return $array1;
}

jrough

thanks, very much, i'm still learning all the array functions.