php 冒泡排序函数

冒泡排序算法是最基本的c语言算法之一，作为万能小强php实现起来自然也不成问题。

/*
 * bubblesort() 冒泡排序算法
 * 虽然简单但效率不高^_^
 *
 */
function bubblesort( &$a1 )
{
	if ( !is_array($a1) )
	{ return false; }
	$len = count($a1);
	// go down array and get an element
	for( $i = 0; $i < $len; $i++ )
	{
		// check everything above element
		// if we are larger than swap it
		// with that one
		for ( $j = ($i+1); $j < $len; $j++ )
		{
			if ( $a1[$i] > $a1[$j] )
			{	swap( $a1[$i], $a1[$j] ); }
		}
		// at this point the position at $i is the smallest
		// go to the next one
	}
	return true;
}

if ( !function_exists('swap') )
{
	// quess what this function is for
	function swap( &$a, &$b )
	{
		$h = $a;
		$a = $b;
		$b = $h;
	}
}