删除重复字符 [英] Remove repeating character

问题描述

我如何删除重复字符(例如，删除cakkkke中的字母k，使其成为cake)?

How would I remove repeating characters (e.g. remove the letter k in cakkkke for it to be cake)?

一种简单的方法是遍历字符串中的每个字符，如果该字符不是先前字符的重复，则将字符串中的每个字符附加到新字符串中.

One straightforward way to do this would be to loop through each character of the string and append each character of the string to a new string if the character isn't a repeat of the previous character.

下面的代码可以做到这一点:

Here is some code that can do this:

$newString = '';
$oldString = 'cakkkke';
$lastCharacter = '';
for ($i = 0; $i < strlen($oldString); $i++) {
    if ($oldString[$i] !== $lastCharacter) {
        $newString .= $oldString[$i];
    }
    $lastCharacter = $oldString[$i];
}
echo $newString;

是否可以使用正则表达式或内置函数更简洁地完成相同的事情?

Is there a way to do the same thing more concisely using regex or built-in functions?

推荐答案

使用反向引用

echo preg_replace("/(.)\\1+/", "$1", "cakkke");

输出:

cake

说明:

(.)捕获任何字符

\\1是对第一个捕获组的反向引用.在这种情况下，上面的..

\\1 is a backreferences to the first capture group. The . above in this case.

+使后向引用至少匹配1(以便它匹配aa，aaa，aaaaa，但不匹配a)

+ makes the backreference match atleast 1 (so that it matches aa, aaa, aaaa, but not a)

用$1替换它会在此情况下用第一个捕获组k替换完全匹配的文本kkk.

Replacing it with $1 replaces the complete matched text kkk in this case, with the first capture group, k in this case.

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