PHP字符串排列 [英] php string permutation

问题描述

比方说，我有一个数组，这些数组由这些范围"a-zA-Z0-9"中的字符组成.我想做的是在4个字母的范围内获得所有可能的组合.字符串中可以重复字符.我正在寻找一种蛮力的方法.

这就是我认为迭代的方式:

"aaaa" "aaab" "aaac" ... "9999"

解决方案

以蛮力方式:

$chars = array_merge(range('0', '9'), range('a', 'z'), range('A', 'Z'));
$cnt = count($chars);
$strings = array();
for ($first = 0; $first < $cnt; $first++) {
   for ($second = 0; $second < $cnt; $second++) {
       for ($third= 0; $third< $cnt; $third++) {
           for ($fourth= 0; $fourth < $cnt; $fourth++) {
              $strings[] = $chars[$first] . $chars[$second] . $chars[$third] . $chars[$fourth];
           }
       }
   }
}

您最终将得到一个honkin'大数组，因此您可能希望将一些数据库操作分散到一个循环中，因此$ strings不会太大，并且不会通过达到内存限制来杀死脚本. /p>

Let's say I have an array consisting of characters from these ranges "a-zA-Z0-9". What I want to do is get all possible combinations possible in a 4-letter range. Characters can be repeated in the string. I'm looking for a brute-force way to do it.

This is how I believe the iteration would be:

"aaaa" "aaab" "aaac" ... "9999"

解决方案

In brute-force fashion:

$chars = array_merge(range('0', '9'), range('a', 'z'), range('A', 'Z'));
$cnt = count($chars);
$strings = array();
for ($first = 0; $first < $cnt; $first++) {
   for ($second = 0; $second < $cnt; $second++) {
       for ($third= 0; $third< $cnt; $third++) {
           for ($fourth= 0; $fourth < $cnt; $fourth++) {
              $strings[] = $chars[$first] . $chars[$second] . $chars[$third] . $chars[$fourth];
           }
       }
   }
}

You'll end up with a honkin' big array, so you might want to sprinkle some database operations into one of the loops, so $strings doesn't get too big and kill your script by hitting a memory limit.

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