プロセスアルゴリズムソリューション

$a = array(<br />  1 => 7,<br />  7 => 11,<br />  8 => 7,<br />  9 => 8,<br />  10 => 11,<br />  11 => 12,<br />  12 => NULL,<br />);<br />$i = 1;<br />while(isset($a[$i])) {<br />  $r[$i] = $a[$i]; <br />  $i = $a[$i];<br />}<br />$r[$i] = $a[$i]; <br />var_export($r);<br />

<br />$map = array(<br />    1 => 7,<br />    7 => 11,<br />    8 => 7,<br />    9 => 8,<br />    10 => 11,<br />    11 => 12,<br />    12 => NULL<br />);<br /><br />function getroad($map){<br />    $key = 1;<br />    $result = array();<br />    while($key!=NULL){<br />        $result[$key] = $map[$key];<br />        $key = $map[$key];<br />    }<br />    return $result;<br />}<br /><br />$result = getroad($map);<br /><br />var_export($result);<br />