Forum Topics

            //06. Forum Topics
            var topicsDict = new Dictionary<string, HashSet<string>>();
            string input = Console.ReadLine();

            while (input != "filter")
            {
                string[] inArr = input
                    .Split(new string[] { " -> " }, StringSplitOptions.None);

                string topic = inArr[0];
                if (!topicsDict.ContainsKey(topic))
                {
                    topicsDict.Add(topic, new HashSet<string>());
                }

                string[] tagsArr = inArr[1]
                    .Split(new string[] { ", " }, StringSplitOptions.None);

                foreach (string tag in tagsArr)
                {
                    topicsDict[topic].Add(tag);
                }

                input = Console.ReadLine();
            }

            string[] tagsToFind = Console.ReadLine()
                .Split(new string[] { ", " }, StringSplitOptions.None);

            foreach (var item in topicsDict)
            {
                bool tagsToFindAreContained = tagsToFind.All(t => item.Value.Contains(t));

                //bool tagsToFindAreContained = true;
                //foreach (string tag in tagsToFind)
                //{
                //    if (!item.Value.Contains(tag))
                //    {
                //        tagsToFindAreContained = false;
                //        break;
                //    }
                //}

                if (tagsToFindAreContained)
                {
                    var resultList = item.Value.Select(x => "#" + x).ToList();

                    Console.WriteLine("{0} | {1}",
                        item.Key,
                        string.Join(", ", resultList));
                }
            }