计算字符串中重复出现的0和1

Return false if the repeated occurrence of 0's or 1's in the string is greater than number($k).

I have written a function which works, but I need to optimize it:

<?php
function satisfied($str, $k){
    $stream = $last = $str[0];
    for($i = 1; $i <= strlen($str)-1; $i++){
        if($str[$i] != $last) $last = $stream = $str[$i];
        else $stream .= $str[$i];
        if(strlen($stream) > $k) return false;
    }
    return true;
}

Example:

satisfied("0111", 2) - False
satisfied("0111", 3) - True
satisfied("00111000111", 3) - True
satisfied("00111000111", 4) - True

I wanted to know if I can do this with help of preg_match?

something like:

preg_match('/(0+|1+){'.$k.'}/', "0111");, this is not even close to what i want to achieve.

I want to avoid for loops to optimize the code. Will the preg_match be faster than the function above ? And obviously, you can also suggest me tweaks to my existing function.

Can someone help me out.

You can do it with strpos:

function satisfied($str, $k) {
    return strpos($str, str_repeat('0', $k+1)) === false
        && strpos($str, str_repeat('1', $k+1)) === false;
}

or you can use preg_match with a simple alternation:

function satisfied($str, $k) {
    $k++;
    $pattern = '~0{' . $k . '}|1{' . $k . '}~';
    return !preg_match($pattern, $str);
}

Note that preg_match returns an integer (or false if a problem occurs), but since there is a negation operator, the returned value is casted to a boolean.

You can take the input as character array and Here's exactly what your looking for :

<?php
function printCharMostRepeated($str)
{
    if (!empty($str))
    {
        $max = 0;
        foreach (count_chars($str, 1) as $key => $val)
            if ($max < $val) {
                $max = $val;
                $i = 0;
                unset($letter);
                $letter[$i++] = chr($key);
            } else if ($max == $val)
                $letter[$i++] = chr($key);
        if (count($letter) === 1)
            echo 'The character the most repeated is "'.$letter[0].'"';
        else if (count($letter) > 1) {
            echo 'The characters the most repeated are : ';
            $count = count($letter);
            foreach ($letter as $key => $value) {
                echo '"'.$value.'"';
                echo ($key === $count - 1) ? '.': ', ';
            }
        }
    } else
        echo 'value passed to '.__FUNCTION__.' can\'t be empty';
}

$str  = 'ddaabbccccsdfefffffqqqqqqdddaaa';
printCharMostRepeated($str);