Kata1.cs

using System.Collections.Generic;
using System.Linq;
using System.Net.Http;
using System.Threading.Tasks;
using Newtonsoft.Json;

namespace TestApp
{
    internal class Stuff
    {
        public List<string> toppings { get; set; }
        public uint GetUHash()
        {
            uint hash = 0; 
            foreach (var i in toppings)
            {
                unchecked
                {
                    hash += (uint)i.GetHashCode();
                }
            }
            return hash;
        }
        
    }

    internal class Program
    {
        private static async Task Main(string[] args)
        {
            HttpContent json = (await new HttpClient().GetAsync("http://files.olo.com/pizzas.json")).Content;
            var data = JsonConvert.DeserializeObject<List<Stuff>>(await json.ReadAsStringAsync());

            var result = data
                .GroupBy(x => x.GetUHash())
                .OrderByDescending(x => x.Count())
                .Take(20)
                .ToDictionary(x => x.ToList()[0], x => x.Count());

            var output = string.Join("\n", 
                result.Select((x, i) =>
                    $"{string.Join(",", x.Key.toppings)}"));
            var a = 9;
        }
    }
}