如何在一个100个元素的数组中快速的随机取出50个不重复的元素

$num =0;$array = array(1,2,3,4,5,6,7,8,9);$arr =array();$g    = 5;$tag = true;while($tag){   $count = count($array);   $t = rand(0,1);    if($t==1){        $arr[] = $array[$num];        unset($array[$num]);    }   $num++;   if(count($arr)==$g){    $tag=false;   }   if($num == $count){     $num  = 0;   }}

function swap(&$a, &$b){    $temp = $b;    $b = $a;    $a = $temp;}$result = array();$src = array();for($i = 0 ; $i < 40 ; $i++){    $src[] = $i + 1;}$arr_len = count($src);$count = 20;$index = 0;while($index < $count){    $random = rand(0, $arr_len - $index - 1);    $result[] = $src[$random];    swap($src[$random] , $src[$arr_len - $index - 1]);    $index += 1;}print_r(json_encode($result));print_r(json_encode($src));

$a = range(1, 100);foreach(array_rand($a, 50) as $k) $r[] = $a[$k];echo join(',', $r);

$arr = array(1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8);$arr_uni = array_unique($arr);shuffle($arr_uni);$result = array_slice($arr_uni, 0, 5);print_r($result);