Codility Answers 04

Here is my answer to Cod1l1ty training lesson 04.

CountDiv

function solution($A) {
////  Brute-force way
//    $n = count($A);
//    $max = null;
//    for($p = 0; $p < $n - 2; $p++) {
//        for($q = $p + 1; $q < $n -1; $q++) {
//            for($r = $q + 1; $r < $n; $r++) {
//               $product = $A[$p] * $A[$q] * $A[$r];
//                if($max === null || $max < $product){
//                    $max = $product;
//                }
//            }
//        }
//    }
    
//  Better way
    $p = null;
    $q = null;
    $r = null;
    $p1 = null;
    $q1 = null;
    $r1 = null;
    
    foreach($A as $val){
        if($p === null || $val >= $p) {
            $r = $q;
            $q = $p;
            $p = $val;
        }elseif($q === null || $val >= $q) {
            $r = $q;
            $q = $val;
        }elseif($r === null || $val >= $r) {
            $r = $val;
        }
        if($p1 === null || $val <= $p1) {
            $r1 = $q1;
            $q1 = $p1;
            $p1 = $val;
        }elseif($q1 === null || $val <= $q1) {
            $r1 = $q1;
            $q1 = $val;
        }elseif($r1 === null || $val <= $r1) {
            $r1 = $val;
        }
    }
    
    if($p >= 0){
        if($r <= 0 || $p1 * $q1 > $q * $r) {
            $q = $p1;
            $r = $q1;
        }
    }
    
    return $p*$q*$r;
}

---

Should use merge sort for best performance, but because I didn't know how to do it yet, so I'll leave it like this for now.