Regex optional matching with letters numbers and symbols

Question

I'm looking for a regex pattern with the following particulars

• Case insensitive
• Only 1 letter is valid at a time
• letters be preceded by a number with an optional space
• Any symbol is valid, ie % , @ , / , - etc
• It shouldn't match on 3 whole integer numbers 2342 34534 2342 . however 345345 / 435 or 236 545 is fine
• The pattern needs to match the complete string
• Multiple spaces and underscore will be cleaned up beforehand and not relevant

Matches

"1"
"12"
"12 34"
"12 a 34"
"1a"
"54b"
"32 c"
"43-23"
"45 c/34"
"45/34 d"
"67 / 345"
"23a / 56"
"12 / 56B"

Just to be more specific. The following should not match

"1 3 5"
"34 a a"
"34b s"
"56/v"
"234 / a"
"234a/a"
"34b 456s"
"34b/456s"
"34b / 456s"

My current attempt is ^\\d+[\\s]?[az\\W]?[\\s]?[\\W]?[\\s]?\\d+?[az]?$

You can see a demo here

Although I'll most likely need more than one pattern (for the letters either side of the symbol), my main problem is trying to get the ? to work correctly, ie with the current pattern id expect to get more positives

Update

The current regex produces the following results.

Good list
-------------
False - 1 <= this should match
True - 12 34
True - 12 a 34
False - 1a <= this should match
True - 54b
False - 32 c <= this should match
True - 43-23
True - 45c/34
True - 45/34d
True - 67 / 345
True - 23a / 56
True - 12 / 56b

Bad list
-------------
False - 1 3 5
False - 34 a a
False - 34b s
False - 234a/a
True - 34b 456s <= these are false positives only because they have 2 letters
True - 34b/456s
True - 34b / 456s

Ignoring the false positives, which I can fix by creating 2 patterns, I'm stuck on why the current regex is not matching on those pointed out.

Answer 1

Guessing from your description, I suggest the following pattern:

^\d+\s?(?:\W\s?\d+(?:\s?[a-z])?|(?:\d+\s?)?[a-z]?|[a-z]\s?\W\s?\d+)$

Demo

Sample Code:

using System;
using System.Text.RegularExpressions;
using System.Collections.Generic;

public class Program
{
    public static void Main()
    {
        var goodList = new List<string>{"1", "12", "12 34","12 a 34", "1a", "54b", "32 c", "43-23", "45c/34", "45/34d", "67 / 345", "23a / 56", "12 / 56b"};
        var badList = new List<string>{"1 3 5", "34 a a", "34b s", "234a/a", "34b 456s", "34b/456s", "34b / 456s"};
        var pattern = @"^\d+\s?(?:\W\s?\d+(?:\s?[a-z])?|(?:\d+\s?)?[a-z]?|[a-z]\s?\W\s?\d+)$";
        var regex = new Regex(pattern);
        Console.WriteLine("Good list");
        Console.WriteLine("-------------");
        foreach (var item in goodList)
        {
            Console.WriteLine(string.Format("{0} - {1}", regex.IsMatch(item), item));
        }

        Console.WriteLine();
        Console.WriteLine("Bad list");
        Console.WriteLine("-------------");
        foreach (var item in badList)
        {
            Console.WriteLine(string.Format("{0} - {1}", regex.IsMatch(item), item));
        }
    }
}

Answer 2

You may try this too.

(?im)^(?!(?:\d+\s){2}\d+\s*$)[^a-z\n]*(?:(?:\d\s?)[a-z])?[^a-z\n]*$

Demo in .NET regex tester ,,, please click tabs, [table] and [context] for more infomation of matching.