<?php
 
function markup_same_route($a, $b) {
	foreach ($b as $i) {
		if (array_search($i, $a)) {
			$c[] = '★' . $i . '★';
		} else {
			$c[] = $i;
		}
	}
 
	$s = implode('|', $c);
 
	$n = count($b);
	while ($n > 0) {
		$s2 = preg_replace('/→(.*?)★\|★\1→/', '→\1|\1→', $s);
		if ($s == $s2) {
			break;
		} else {
			$s = $s2;
		}
		$n = $n - 1;
	}
 
	$c = explode('|', $s);
 
	return $c;
}
 
// test
 
$a[1]='北千住→日暮里';
$a[2]='日暮里→上野';
$a[3]='上野→秋葉原';
$a[4]='秋葉原→つくば';
$a[5]='つくば→茨城';
$a[6]='茨城→東京';
$a[7]='東京→大阪';
$a[8]='大阪→名古屋';
$a[9]='名古屋→京都';
$a[10]='京都→大宮';
 
$b[1]='北千住→日暮里';
$b[2]='渋谷→代々木';
$b[3]='上野→秋葉原';
$b[4]='秋葉原→つくば';
$b[5]='大阪→名古屋';
$b[6]='名古屋→一宮';
$b[7]='東京→大阪';
$b[8]='大阪→名古屋';
$b[9]='名古屋→京都';
$b[10]='京都→梅田';
 
$c = markup_same_route($a, $b);
print_r($c);
 
?>
 

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