ヒルクライムによる最小コストを求める関数。コスト関数を入れ替えれば、他の問題においても最小、最大値を求めることができる。

PHPで学ぶ集合知プログラミング5.5

function hillclimb($domain, $origin, $people, $flights, $destination) {
    $r = array();
    for($s = 0; $s < count($domain); $s++) {
        $r[] = rand($domain[$s][0], $domain[$s][1]);
    }
    while(1){
        $neighbors = array();
        for ($k = 0; $k < count($domain); $k++) {
            if($r[$k] > $domain[$k][0]) {
                $neighbors[] = array_replace($r, array($k => $r[$k]-1));
            }

            if($r[$k] < $domain[$k][1]) {
                $neighbors[] = array_replace($r, array($k => $r[$k]+1));
            }
        }

        $current = schedulecost($r, $origin, $people, $flights, $destination);
        $best = $current;
        for ($p = 0; $p < count($neighbors); $p++) {
            $cost = schedulecost($neighbors[$p], $origin, $people, $flights, $destination);
            if ( $cost < $best ) {
                $best = $cost;
                $r = $neighbors[$p];
            }
        }
        if( $best == $current ) {
            break;
        }
    }
    return $r;
}

$result = hillclimb($domain, $origin, $people, $flights, $destination);
var_dump($result);
$cost = schedulecost($result, $origin, $people, $flights, $destination);
var_dump($cost);
$schedule = printschedule($result, $people, $flights, $destination);