// RE: https://stackoverflow.com/q/75986766/1690217

​

using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Demo LexicographicToAlphaNumeric Sorting:");

        var tests = new string [] {

            "Bird 10",

            "Bird 2",

            "Bird 1",

            "20Lions",

            "5Lions",

            "red10blue",

            "Red9blue",

            "red100Blue"

        };

            foreach(var x in tests.Select(x => new { Value=x, SortKey = LexicographicToAlphaNumeric(x)}).OrderBy(x => x.SortKey))

                Console.WriteLine("{0}   ({1})", x.Value.PadRight(15), x.SortKey);

        Console.WriteLine();

        Console.WriteLine("Demo longer numberics");

        Console.WriteLine( LexicographicToAlphaNumeric("Bird 10000",7));

        Console.WriteLine( LexicographicToAlphaNumeric("Bird 2000",7)); 

        Console.WriteLine( LexicographicToAlphaNumeric("Bird 1000",7));

    }

    /// <summary> Pad numeric portions of a string to allow natural lexicographic sorting to behave like numerical sorting for the numeric components</summary>

    /// <remarks> using the same categorization technique to simplify the explanation, have not tested this for performance, and I just love the name ;)</remarks>

    /// <param name="value">The string value to pad the numbers in</param>

    /// <param name="size">The number of digits to pad the numeric values out to, by default 3 digits</param>

    /// <returns> alphanumeric string that so that "Bird 2" becomes "Bird 02", to allow "Bird 2" to be sorted before "Bird 10"<returns>

    public static string LexicographicToAlphaNumeric(string value, int size = 3)

    {

        // exit if there is nothing to process.

        if (String.IsNullOrWhiteSpace(value)) return value;

        int groupId = 0;

        bool isNumberGroup = false;

        return String.Join("", value.Select((c, index) => {

            var isNumber = Char.IsDigit(c); // NOTE: will not support decimals

            if( isNumber != isNumberGroup)

            {

                groupId ++;

                isNumberGroup = isNumber;

            }

            return new { c, isNumber, groupId, index };

        })

            .GroupBy(c => c.groupId)

            .Select(g => g.First().isNumber ? new string(g.Select(x => x.c).ToArray()).PadLeft(size, '0') : new string(g.Select(x => x.c).ToArray())));

    }

}