将字符串转换为不同字符发生的数组 [英] Convert string to array at different character occurence

问题描述

考虑我有这个字符串'aaaabbbaaaaaabbbb'我想将其转换为数组，以便获得以下结果

Consider I have this string 'aaaabbbaaaaaabbbb' I want to convert this to array so that I get the following result

$array = [
    'aaaa',
    'bbb',
    'aaaaaa',
    'bbbb'   
]

如何在PHP中执行此操作？

How to go about this in PHP?

推荐答案

我已经写了一行只使用 preg_split（）生成预期的结果，没有浪费的内存（没有阵列膨胀）：

I have written a one-liner using only preg_split() that generates the expected result with no wasted memory (no array bloat):

代码（演示）：

$string='aaaabbbaaaaaabbbb';
var_export(preg_split('/(.)\1*\K/',$string,NULL,PREG_SPLIT_NO_EMPTY));

输出：

array (
  0 => 'aaaa',
  1 => 'bbb',
  2 => 'aaaaaa',
  3 => 'bbbb',
)

模式：

(.)         #match any single character
\1*         #match the same character zero or more times
\K          #keep what is matched so far out of the overall regex match

真正的魔法发生在 \K ，如需更多阅读，请此处。
preg_split（）中的 NULL 参数表示无限制匹配。这是默认行为，但它需要在函数中保留它的位置，以便下一个参数被适当地用作标志
最后一个参数是 PREG_SPLIT_NO_EMPTY 可以删除任何空的匹配。

The real magic happens with the \K, for more reading go here. The NULL parameter in preg_split() means "unlimited matches". This is the default behavior but it needs to hold its place in the function so that the next parameter is used appropriately as a flag The final parameter is PREG_SPLIT_NO_EMPTY which removes any empty matches.

Sahil的 preg_match_all（）方法 preg_match_all（'/（。）\\ \\ 1 {1，} /'，$ string，$ matches）; 是一个很好的尝试，但由于两个原因而不完美：

Sahil's preg_match_all() method preg_match_all('/(.)\1{1,}/', $string,$matches); is a good attempt but it is not perfect for two reasons:

第一个问题是他使用 preg_match_all（）返回两个子阵列，这是必要结果的两倍。

The first issue is that his use of preg_match_all() returns two subarrays which is double the necessary result.

当 $ string =abbbaaaaaabbb; 时，会显示第二个问题。他的方法将忽略第一个孤单的角色。这是它的输出：

The second issue is revealed when $string="abbbaaaaaabbbb";. His method will ignore the first lone character. Here is its output:

Array (
    [0] => Array
        (
            [0] => bbb
            [1] => aaaaaa
            [2] => bbbb
        )
    [1] => Array
        (
            [0] => b
            [1] => a
            [2] => b
        )
)

Sahil的第二个尝试产生正确的输出，但需要更多的代码。一个更简洁的非正则表达式解决方案可能如下所示：

Sahil's second attempt produces the correct output, but requires much more code. A more concise non-regex solution could look like this:

$array=str_split($string);
$last="";
foreach($array as $v){
    if(!$last || strpos($last,$v)!==false){
        $last.=$v;
    }else{
        $result[]=$last;
        $last=$v;
    }
}
$result[]=$last;
var_export($result);

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