CODEWITHSUNDEEP
phparraysloops
ssuperczynski
ssuperczynski

Reputation: 3416

remove every Nth letter (loop)

I found here many responses for my question but I cat't find exactly what I am looking for.
I have to remove every 4th digit from an array, but beginning and the end making a circle, so If I remove 4th digit in next loop It's gonna be another digit (maybe 4th maybe 3rd) It's depend how many digit we have in string

$string = "456345673474562653265326";
$chars = preg_split('//', $string, -1, PREG_SPLIT_NO_EMPTY);
$result = array();
for ($i = 0; $i < $size; $i += 4) 
{
    $result[] = $chars[$i];
}

Upvotes: 3

Views: 1845

Answers (4)

Susam Pal
Susam Pal

Reputation: 34284

<?php
$string = "abcdef";
$chars = str_split($string);

$i = 0;
while (count($chars) > 1) {
    $i += 3;
    $n = count($chars);
    if ($i >= $n)
        $i %= $n;

    unset($chars[$i]);
    $chars = array_values($chars);

    echo "DEBUG LOG: n: $n, i: $i; s: " . implode($chars, '') . "\n";
}
?>

Output:

DEBUG LOG: n: 6, i: 3; s: abcef
DEBUG LOG: n: 5, i: 1; s: acef
DEBUG LOG: n: 4, i: 0; s: cef
DEBUG LOG: n: 3, i: 0; s: ef
DEBUG LOG: n: 2, i: 1; s: e

Upvotes: 0

Mark Baker
Mark Baker

Reputation: 212452

A non-regexp solution

$string = "123412341234";
$n = 4;
$newString = implode('',array_map(function($value){return substr($value,0,-1);},str_split($string,$n)));

var_dump($newString);

Upvotes: 0

ARRG
ARRG

Reputation: 2496

You can try this (my PHP is rusty so I'm not sure whether erasing this way will work):

$string = "123412341234";
$result = array();
$n = 4; // Number of chars to skip at each iteration

$idx = 0; // Index of the next char to erase
$len = strlen($string);
while($len > 1) { // Loop until only one char is left
    $idx = ($idx + $n) % $len; // Increase index, restart at the beginning of the string if we are past the end
    $result[] = $string[$idx];      
    $string[$idx] = ''; // Erase char
    $idx--; // The index moves back because we erased a char
    $len--;
}

Upvotes: 0

zysoft
zysoft

Reputation: 2358

You could try doing this with preg_replace:

$string = "12345678901234567890";
$result = preg_replace("/(.{3})\d/", "$1", $string);

Upvotes: 3

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