冒泡排序的实现

升序

// 方法1

$a = [2, 4, 3, 1, 7, 5];

$c = count($a);

for ($i = 0; $i < $c - 1; $i++) {
    for ($j = $i + 1; $j < $c; $j++) {
        if ($a[$i] > $a[$j]) {
            $t     = $a[$i];
            $a[$i] = $a[$j];
            $a[$j] = $t;
        }
    }
}

print_r($a);


// 方法2

$a = [2, 4, 3, 1, 7, 5];

$c = count($a);

for ($i = 1; $i < $c; $i++) {
    for ($j = 0; $j < $c - $i; $j++) {
        if ($a[$j] > $a[$j + 1]) {
            $t         = $a[$j];
            $a[$j]     = $a[$j + 1];
            $a[$j + 1] = $t;
        }
    }
}

print_r($a);