查找字符串中字符的多个非连续出现 [英] Find multiple, non consecutive, occurrences of a character in string

问题描述

有人可以帮我写RegEx表达式吗，它可以检查一个字符串是否包含一个以上的大写字母(或小写字母，无关紧要)字母，但不能连续出现.我需要在一个字符串中至少出现两次(甚至更好的n次).如果n = 2，则有效情况为密码，密码或密码.

Can somebody please help me write RegEx expression which can check if a string contains more than one occurrence of a uppercase (or lowercase, doesn't matter) letter but not in a row. I need to have at least two (or even better n) occurrences in a string. If n=2 valid situations would be PassWord or PAssword or PASSWord.

当我尝试使用此/(?=([A-Z] {2,3}))/g 时，它匹配PassWOrd，但不匹配PassWord.

When I tried this /(?=([A-Z]{2,3}))/g it matched PassWOrd but not PassWord.

对我来说奇怪的是，它也与PaSSWOrd相匹配.我以为{2,3}中的3实际上意味着最多将匹配3个大写字符.SSWO为什么匹配?

What is strange to me is that it also matched PaSSWOrd. I thought 3 in {2,3} actually means that no more that 3 Uppercase characters will be matched. Why is SSWO matched?

我尝试了类似的变体，但没有一个对我有用(因为我对RegEx不太熟悉，这并不奇怪).

I tried similar variations but non of them worked for me (nothing strange as i'm not very familiar with RegEx).

可以使用RegEx做到吗?

Can this be done using RegEx?

推荐答案

(?=([AZ] {2,3}))正则表达式匹配2到3个连续大写ASCII字母字符串中的任意位置.您想匹配一个仅包含2到3个大写ASCII字母的字符串，而不必连续.

The (?=([A-Z]{2,3})) regex matches 2 to 3 consecutive uppercase ASCII letters anywhere inside a string. You want to match a string that only contains 2 to 3 uppercase ASCII letters, not necessarily consecutively.

要匹配仅包含两个大写ASCII字母(不多不少)的字符串，请使用以下表达式:

To match a string that only contains two uppercase ASCII letters (no more no less), use the following expression:

^(?:[^A-Z]*[A-Z]){2}[^A-Z]*$

或者，如果您只允许在整个字符串中使用ASCII字母:

Or, if you only allow ASCII letters in the whole string:

^(?:[a-z]*[A-Z]){2}[a-z]*$

请参见 模式详细信息

• ^ -字符串的开头
• (?:[^ A-Z] * [A-Z]){2} -正好发生2次
  • [^ A-Z] * -零个或多个字符(ASCII大写字母除外)
  • [A-Z] -一个ASCII大写字母
  • ^ - start of string
  • (?:[^A-Z]*[A-Z]){2} - exactly 2 consequent occurrences of
    • [^A-Z]* - zero or more chars other than ASCII uppercase letters
    • [A-Z] - one ASCII uppercase letter

    在C#中，使用

    var strs = new List<string> { "PassWord", "PAssword", "PASSWord"};
    var n = 2;
    var pat = $@"^(?:[^A-Z]*[A-Z]){{{n}}}[^A-Z]*$";
    foreach (var s in strs) {
        Console.WriteLine("{0}: {1}", s, Regex.IsMatch(s, pat));
    }
    

    结果:

    PassWord: True
    PAssword: True
    PASSWord: False
    

    请参见在线演示

    请注意，如果您需要在字符串中要求2个大写ASCII字母(其中其他字符可以是任何字符)，则不需要正则表达式，请使用LINQ:

    Note that in case you need to require 2 uppercase ASCII letters in a string where other chars can be any chars, you do not need a regex, use LINQ:

    var strs = new List<string> { "PassWord", "PAssword", "PASSWord"};
    var n = 2;
    foreach (var s in strs) {
        var res = s.Count(c => (c >= 65 && c <= 90));
        Console.WriteLine("{0}: {1}", s, res == 2);
    }
    

    请参见另一个演示. .Count(c =>(c> = 65&& c< = 90))部分将计算字符串中任意位置的大写ASCII字母，而 res == 2 将返回一个布尔结果，无论该数字是否等于2.可以轻松调整以进行数字范围检查.

    See another demo. The .Count(c => (c >= 65 && c <= 90)) part will count the uppercase ASCII letters anywhere in the string, and res==2 will return a boolean result, whether the number is equal to 2 or not. It can be adjusted for a numeric range check easily.

    如果需要Unicode兼容性，请将 .Count(c =>(c> = 65& c< = 90))替换为 .Where(Char.IsUpper).

    If you need Unicode compatibility, replace .Count(c => (c >= 65 && c <= 90)) with .Where(Char.IsUpper).

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