Question

我在实施Lawler算法方面遇到了一些麻烦，但多亏了SO和200点声望，我终于设法编写了一个有效的实现：

Lawler's Algorithm Implementation Assistance

我觉得我在那里使用了太多的变量和循环，所以我试图重构代码。它应该更简单，更短，但仍然可读。

为此制作课程是否有意义？欢迎任何建议甚至帮助重构这段代码：

<?php

/*
 * @name Lawler's algorithm PHP implementation
 * @desc This algorithm calculates an optimal schedule of jobs to be
 *       processed on a single machine (in reversed order) while taking
 *       into consideration any precedence constraints.
 * @author Richard Knop
 *
 */

$jobs = array(1 => array('processingTime' => 2,
                         'dueDate'        => 3),
              2 => array('processingTime' => 3,
                         'dueDate'        => 15),
              3 => array('processingTime' => 4,
                         'dueDate'        => 9),
              4 => array('processingTime' => 3,
                         'dueDate'        => 16),
              5 => array('processingTime' => 5,
                         'dueDate'        => 12),
              6 => array('processingTime' => 7,
                         'dueDate'        => 20),
              7 => array('processingTime' => 5,
                         'dueDate'        => 27),
              8 => array('processingTime' => 6,
                         'dueDate'        => 40),
              9 => array('processingTime' => 3,
                         'dueDate'        => 10));
// precedence constrainst, i.e job 2 must be completed before job 5 etc
$successors = array(2=>5,
                    7=>9);
$n = count($jobs);
$optimalSchedule = array();

for ($i = $n; $i >= 1; $i--) {

    // jobs not required to precede any other job
    $arr = array();
    foreach ($jobs as $k => $v) {

        if (false === array_key_exists($k, $successors)) {
            $arr[] = $k;
        }

    }

    // calculate total processing time
    $totalProcessingTime = 0;
    foreach ($jobs as $k => $v) {
        if (true === array_key_exists($k, $arr)) {
            $totalProcessingTime += $v['processingTime'];
        }
    }

    // find the job that will go to the end of the optimal schedule array
    $min = null;
    $x = 0;
    $lastKey = null;
    foreach($arr as $k) {
        $x = $totalProcessingTime - $jobs[$k]['dueDate'];
        if (null === $min || $x < $min) {
            $min = $x;
            $lastKey = $k;
        }
    }

    // add the job to the optimal schedule array
    $optimalSchedule[$lastKey] = $jobs[$lastKey];
    // remove job from the jobs array
    unset($jobs[$lastKey]);
    // remove precedence constraint from the successors array if needed
    if (true === in_array($lastKey, $successors)) {
        foreach ($successors as $k => $v) {
            if ($lastKey === $v) {
                unset($successors[$k]);
            }
        }
    }

}

// reverse the optimal schedule array and preserve keys
$optimalSchedule = array_reverse($optimalSchedule, true);

// add tardiness to the array
$i = 0;
foreach ($optimalSchedule as $k => $v) {
    $optimalSchedule[$k]['tardiness'] = 0;
    $j = 0;
    foreach ($optimalSchedule as $k2 => $v2) {
        if ($j <= $i) {
            $optimalSchedule[$k]['tardiness'] += $v2['processingTime'];
        }
        $j++;
    }
    $i++;
}

echo '<pre>';
print_r($optimalSchedule);
echo '</pre>';

Answer 1

我会把它变成一个班级。当所有必要的变量都被封装为类成员时，我发现重构算法更容易，而不是记住每次提取方法时我必须传入和传出的值。

您应该在构造函数中设置算法的输入，然后使用通用的execute方法。这样可以更轻松地符合命令和策略模式。

将所有循环和条件体转换为单独的受保护函数。通过适当的命名，可以极大地提高可读性，并使通过继承更改算法变得更加容易。

帮助重构PHP代码

1 个答案: