Counting number of occurrences of characters from array in string?

Question

I'm writing code to determine whether a password contains enough punctuation characters.

How do I count the number of occurrences of any characters from a set?

Something along these lines:

private const string nonAlphaNumericCharSet = "#*!?£$+-^<>[]~()&";
...
public static bool PasswordMeetsStrengthRequirements(string password)
{
    return password.Length >= MINIMUM_PASSWORD_LENGTH && password.NumberOfOccurences(nonAlphaNumericCharSet.ToCharArray()) >= MINIMUM_NONALPHANUMERIC_CHARS;
}

Bonus points for an elegant linq solution.

@Oliver: I guess Black Knight will be awarding a bounty (after the 24 hour wait period). — Chris Sinclair, May 22 '13 at 09:57
I was thinking about awarding upvotes. And of course my own personal gratitude ;). However, if people think an answer deserves a bounty then I'll award one. — Kev, May 22 '13 at 09:58
Maybe this will help http://stackoverflow.com/questions/11569951/elegant-way-to-count-alphanumeric-chars-in-a-string — Liviu, May 22 '13 at 10:07

score 17 · Accepted Answer · answered May 22 '13 at 09:51

17

How do I count the number of occurences of any characters from a set?

var count = password.Count(nonAlphaNumericCharSet.Contains);

answered May 22 '13 at 09:51

I4V

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+1, slick ..........., for those like me, its simpler form would be: `var temp = password.Count(r=> nonAlphaNumericCharSet.Contains(r));` – Habib May 22 '13 at 09:54
Thanks for the explanation. I was just wondering what the simpler form would be. – Kev May 22 '13 at 09:56
1

@Carra, yes by just 6 minutes. – Habib May 22 '13 at 10:02
That and it's also more efficient :) – Carra May 22 '13 at 10:31

score 1 · Answer 2 · answered May 22 '13 at 09:51

1

you can count like this

int count = "he!l!l!o".Split('!').Length - 1;

it will return 3.

Using linq

int count="he!l!l!o".Count(x => x == '!');

answered May 22 '13 at 09:51

Mogli

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score 1 · Answer 3 · answered May 22 '13 at 09:58

Here's an example:

private const string nonAlphaNumericCharSet = "#*!?£$+-^<>[]~()&";

public static bool PasswordMeetsStrengthRequirements(string password)
{
    return password.Count(x => nonAlphaNumericCharSet.Contains(x)) > 2 && password.Length > 1;
}

public static void Main()
{
    PasswordMeetsStrengthRequirements("Test").Dump();
    PasswordMeetsStrengthRequirements("Test#").Dump();
    PasswordMeetsStrengthRequirements("(Test#").Dump();
    PasswordMeetsStrengthRequirements("(Te[st#").Dump();
}

giammin · Answer 4 · 2013-05-22T12:35:18.420

1

what about a RegExp

Regex rgx = new Regex(@"^(?=.*(\W.*){4,}).{8,}$", RegexOptions.Compiled);
bool validPassword = rgx.IsMatch(password);

4=min not word/digit char

8= min password leght

Linq may be considered elegant (it isn't IMHO) but at which performance cost?

------------Update after comment---------------

if you want to match a subset of chars you have to replace \W with []

[]= range of chars

some chars have to be escaped with \

in your case: [#\*!\?£\$\+-\^\<\>\[\]~&]

there you can find a regular expression cheat sheet

edited May 22 '13 at 12:35

answered May 22 '13 at 10:37

giammin

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Thanks. Regexs are powerful but I'm not very good at them. It's important in this case however, to only match punctuation from a predefined set, not just all punctuation. How would I do that with a regex? – Kev May 22 '13 at 11:26
@BlackKnight just updated my answer. I'm not good at regular expression either. I find very usefull this cheatsheet: https://github.com/shadowbq/Cheat-Sheets/blob/master/regex/regular-expressions-cheat-sheet-v2.pdf i have printed it and it is always near my desk! – giammin May 22 '13 at 12:42

Counting number of occurrences of characters from array in string?

4 Answers4