Strings Mix, C# - rextester

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            string s1 = " In many languages";
            string s2 = " there's a pair of functions";
            Console.WriteLine("1:aaa/1:nnn/1:gg/2:ee/2:ff/2:ii/2:oo/2:rr/2:ss/2:tt");
            Console.WriteLine();
            string s3 = StringsMix(s1, s2);
            Console.WriteLine(s3);
        }
	
        public static string StringsMix(string s1, string s2)
        {
            StringBuilder sb = new StringBuilder();
            char[] s1Chars = s1.Where(x => char.IsLower(x)).OrderBy(x => x).ToArray();
            char[] s2Chars = s2.Where(x => char.IsLower(x)).OrderBy(x => x).ToArray();
            
            for (int i = 97; i < 122; i++){
                char[] s1Ch = s1.Where(x => x.Equals((char)i)).ToArray();
                char[] s2Ch = s2.Where(x => x.Equals((char)i)).ToArray();
                int s1Count = s1Ch.Length;
                int s2Count = s2Ch.Length;
                
                if (s1Count > s2Count)
                {
                    string chars = new String(s1Ch);
                    sb.Append("1:" + chars + "/");
                }
                else if (s2Count > s1Count)
                {
                    string chars = new String(s2Ch);
                    sb.Append("2:" + chars + "/");
                }
                else if (s1Count == s2Count)
                {
                    string chars = new String(s1Ch);
                    sb.Append("=:" + chars + "/");
                }
            }
            string final = String.Empty;
            var specialOrder = "12=";
            string[] strings = sb.ToString().Split('/');
            
            final = String.Join("/", strings);
            strings = final.Split('/').Where(x => x.Length > 3).Select(x => x).ToArray();
            final = String.Join("/", strings);
            strings = final.Split('/').OrderByDescending(x => x.Length)
                                      .ThenBy(s => specialOrder.IndexOf(s[0]))
                                      .ThenBy(s => s).ToArray();
            final = String.Join("/", strings);
            return final;
        }
    }
}

Show compiler warnings [ + ] Show input
Compilation time: 0,19 sec, absolute running time: 0,13 sec, cpu time: 0,14 sec, average memory usage: 15 Mb, average nr of threads: 3