生成100w个小写的英文数字混搭的字符串，多少位才能保证不重复
生成100w个英文数字混搭的字符串 多少位怎么写才能最大限度保证不重复 请教一下
回复讨论(解决方案)
10个数字、26个大写字母、26个小写字母，共 62 中状态
即可视为 62 进制数
pow(62, 4) = 14776336
即当连续递增的情况下，14776336 个之后才会出现重复
远远满足你的需要
哦，没注意你只能是小写字母
那就是
pow(36, 4) = 1679616
也还是能够满足的
哦，没注意你只能是小写字母
那就是
pow(36, 4) = 1679616
也还是能够满足的
这样写产生9位的随机字符串 100w 应该没问题吧
/* * 随机字符串 */ function random_str($length) { $arr = array_merge(range('a', 'z'),range(0, 9)); $str = ''; $arr_len = count($arr); for ($i = 0; $i < $length; $i++) { $rand = mt_rand(0, $arr_len-1); $str.=$arr[$rand]; } return $str; } 这100w字符串 我想分几次生成 1次大约10w个 多次调用这个函数 这样的逻辑会产生重复吗
谢谢斑竹的热心帮忙 我明白了
不能猜测，应该验证一下
set_time_limit(0);mysql_connect();mysql_select_db('test');mysql_query('create temporary table a (ch varchar(9))');$len = 1000000;for($i=0; $i<$len; $i++) { $c = random_str(9); mysql_query("insert into a values ('$c')") or die(mysql_error());}$rs = mysql_query('select ch, count(*) as cnt from a group by 1 having cnt>1') or die(mysql_error());while($r = mysql_fetch_assoc($rs)) { echo join(':', $r), PHP_EOL;}
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