Sabrina Markon - Algorithms - For a given integer (from STDIN), convert to binary then find out the greatest number of 1's in a row in the binary number.

algorithm-binary-how-many-ones-in-a-row.php

<?php
$handle = fopen ("php://stdin","r");
fscanf($handle,"%d",$n);

function addToStack($x, &$stack) {
    $remainder = $x % 2;
    $nextx = ($x - $remainder)/2;
    array_unshift($stack, $remainder);
    if ($nextx >= 1) {
        addToStack($nextx, $stack);
    } else {  
        return $stack;
    }
}
$stack = array();
addToStack($n, $stack);

$count = 0; // running total of 1s in a row.
$highestcount = 0; // highest total of 1s in a row before a 0 is encountered.

for ($i = 0; $i < count($stack); $i++) {
    
    if ($stack[$i] === 1) {
        // add to running count of 1s and totalcount:
        $count++;
    } else {
        // Every time a zero is encountered AND after the for loop finishes to consider array that ends in groups of 1s:
        // if count is bigger than the existing highestcount (which is zero for the first set of 1s encountered),
        // assign it to highestcount as the new highest total of 1s in a row:
        if ($count > $highestcount) {
            $highestcount = $count;
        }
        // we found a 0 so reset the running total:
        $count = 0;
    }
}

if ($count > $highestcount) {
    $highestcount = $count;
}

echo $highestcount;