Find and replace duplicates in Array

Question

I need to make app with will fill array with some random values, but if in array are duplicates my app not working correctly. So I need to write script code which will find duplicates and replace them with some other values. Okay so for example i have an array:

<?PHP
$charset=array(123,78111,0000,123,900,134,00000,900);

function arrayDupFindAndReplace($array){

// if in array are duplicated values then -> Replace duplicates with some other numbers which ones I'm able to specify.
return $ArrayWithReplacedValues;
}
?>

So result shall be the same array with replaced duplicated values.

You might want to check out array_unique() and array_replace() before needing to write your own method first; they might be just what you need. — newfurniturey
– newfurniturey, Commented Nov 4, 2012 at 3:03
I check that and it don't pass my needs. Thanks for trying to help me. — xZero
– xZero, Commented Nov 4, 2012 at 3:25
This question would be more clear if you expressed the replacement string(s) that you would like to use and your exact expected result. A minimal reproducible example @xZero — mickmackusa
– mickmackusa ♦, Commented Aug 16, 2020 at 12:57

Steven Liao · Accepted Answer · 2012-11-04 07:14:45Z

You can just keep track of the words that you've seen so far and replace as you go.

// words we've seen so far
$words_so_far = array();
// for each word, check if we've encountered it so far
//    - if not, add it to our list
//    - if yes, replace it
foreach($charset as $k => $word){
    if(in_array($word, $words_so_far)){
        $charset[$k] = $your_replacement_here;
    }
    else {
        $words_so_far[] = $word;
    }
}

For a somewhat-optimized solution (for cases where there are not that many duplicates), use array_count_values() (reference here) to count the number of times it shows up.

// counts the number of words
$word_count = array_count_values($charset);
// words we've seen so far
$words_so_far = array();
// for each word, check if we've encountered it so far
//    - if not, add it to our list
//    - if yes, replace it
foreach($charset as $k => $word){
    if($word_count[$word] > 1 && in_array($word, $words_so_far)){
        $charset[$k] = $your_replacement_here;
    }
    elseif($word_count[$word] > 1){
        $words_so_far[] = $word;
    }
}

Sergey Onishchenko · Accepted Answer · 2013-06-17 20:12:15Z

Here the example how to generate unique values and replace recurring values in array

function get_unique_val($val, $arr) {
    if ( in_array($val, $arr) ) {
        $d = 2; // initial prefix 
        preg_match("~_([\d])$~", $val, $matches); // check if value has prefix
        $d = $matches ? (int)$matches[1]+1 : $d;  // increment prefix if exists

        preg_match("~(.*)_[\d]$~", $val, $matches);

        $newval = (in_array($val, $arr)) ? get_unique_val($matches ? $matches[1].'_'.$d : $val.'_'.$d, $arr) : $val;
        return $newval;
    } else {
        return $val;
    }
}

function unique_arr($arr) {
    $_arr = array();
    foreach ( $arr as $k => $v ) {
        $arr[$k] = get_unique_val($v, $_arr);
        $_arr[$k] = $arr[$k];
    }
    unset($_arr);

    return $arr;
}




$ini_arr = array('dd', 'ss', 'ff', 'nn', 'dd', 'ff', 'vv', 'dd');

$res_arr = unique_arr($ini_arr); //array('dd', 'ss', 'ff', 'nn', 'dd_2', 'ff_2', 'vv', 'dd_3');

Full example you can see here webbystep.ru

Tim Dearborn · Accepted Answer · 2012-11-04 03:04:16Z

1

Use the function array_unique()

See more info at http://php.net/manual/en/function.array-unique.php

answered Nov 4, 2012 at 3:04

Tim Dearborn

1,1777 silver badges18 bronze badges

2 Comments

xZero Over a year ago

Thans for trying to help me. But it just removes duplicates. I wanna replace duplicates instead of removing it.

mickmackusa Over a year ago

This will potentially reduce the size of the array -- the OP doesn't want this.

ajacian81 · Accepted Answer · 2012-11-04 03:03:29Z

-1

$uniques = array();
foreach ($charset as $value) 
   $uniques[$value] = true;
$charset = array_flip($uniques);

answered Nov 4, 2012 at 3:03

ajacian81

7,6299 gold badges54 silver badges66 bronze badges

2 Comments

xZero Over a year ago

Thanks. But how to use it? For example where to specify with which values duplicates will be replaced?

mickmackusa Over a year ago

This will potentially reduce the size of the array -- the OP doesn't want this.

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