Peaks Demo Task at Codility.com

Codility.com Tests 100/100 Solutions

Lesson 8 –  Prime and composite numbers – Peaks demo task solution code written in php. Gives 100/100 score at the time of publishing.

The description of the problem is copyrighted, so please see the following link for it: https://codility.com/demo/take-sample-test/peaks

Solution in php:

function solution($A) {
    $n = count($A);
    if ($n <= 2) {
        return 0;
    }
    $sum = array_fill(0,$n,0);
    $last = -1;
    $D = 0;
    $sum[0] = 0;
    for ($i = 1; $i + 1 < $n; ++$i) {
        $sum[$i] = $sum[$i - 1];
        if (($A[$i] > $A[$i - 1]) && ($A[$i] > $A[$i + 1])) {
            $D = max($D, $i - $last);
            $last = $i;
            ++$sum[$i];
        }

    }
    if (($sum[$n - 1] = $sum[$n - 2]) == 0) {
        return 0;
    }
    $D = max($D, $n - $last);
    for ($i = ($D >> 1) + 1; $i < $D; ++$i) {
        if ($n % $i == 0) {
            $last = 0;
            for ($j = $i; $j <= $n; $j += $i) {
                if ($sum[$j - 1] <= $last) {
                    break;
                }
                $last = $sum[$j - 1];
            }
            if ($j > $n) {
                return $n / $i;
            }
        }
    }
    for ($last = $D; $n % $last; ++$last){
        ;
    }
    return intval($n / $last);
}

Given “AS IS”, can be ported from other languages from solutions found on the internet, please use with care.

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