Question

How to shift letters in a string x times by giving an array of shifts in PHP

Answer 1

/*

string = "aaa"
After shifting the first 1 letter by 1 = "baa"
After shifting the first 2 letters by 2 = "dca"
After shifting the first 3 letters by 3 = "gfd"
result = "gfd"

*/

function shifLetters($str, $shifts) {
    $size = count($shifts);
    $arr = str_split($str);
    
    for ($i = $size - 1; $i >= 0; $i--) {
        if ($i + 1 < $size) {
            $shifts[$i] += $shifts[$i + 1];
        }
        
        $shifts[$i] = $shifts[$i] % 26;
        $asciicode = ord($str[$i]) - ord('a');
        $asciicode = $asciicode + $shifts[$i];
        
        if ($asciicode > 25) {
            $asciicode = $asciicode - 26;
        }
        
        $arr[$i] = chr((ord('a') + $asciicode));
    }
    
    return implode($arr);
}

$str = "aaa";
$shifts = array(1, 2, 3);

$str = shifLetters($str, $shifts);

echo $str;



/*
run:

gfd

*/

 

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