using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        IndexTests.CanIndexAndQuery();

        IndexTests.CanUpdate();

        IndexTests.CanDelete();

    }

}

​

    public interface IIndexer {

        void Index(string docId, string text);

        List<string> Query(string term);

        void Delete(string docId);

    }

​

    public class CustomIndexer : IIndexer {

        private readonly Dictionary<string, List<string>> _data;

​

        public CustomIndexer() {

            _data = new Dictionary<string, List<string>>(StringComparer.OrdinalIgnoreCase);

        }

​

        public void Index(string docId, string text) {

            var words = text.Split();

​

            List<string> w;

            if (!_data.TryGetValue(docId, out w)) {

                _data.Add(docId, words.ToList());

            }

            else {

                _data[docId] = w;

                foreach (var t in w) {

                    _data[t].Remove(docId);

                }

            }

            foreach (var term in words) {

                List<string> val;

                if (_data.TryGetValue(term, out val) == false) {

                    val = new List<string>();

                    _data[term] = val;

                }

                val.Add(docId);

            }

        }

​

        public List<string> Query(string term) {

            List<string> val;

            _data.TryGetValue(term, out val);

            return val ?? new List<string>();

        }

​

        public void Delete(string docId) {

            var terms = _data[docId];

​

            _data.Remove(docId);

            foreach (var t in terms) {

                _data[t].Remove(docId);

            }

​

        }

    }

​

    public class Indexer : IIndexer {

​

        private readonly Dictionary<string, List<string>> _terms;

        private readonly Dictionary<string, string[]> _docIds;

​

        public Indexer() {

            _terms = new Dictionary<string, List<string>>(StringComparer.OrdinalIgnoreCase);

            _docIds = new Dictionary<string, string[]>(StringComparer.OrdinalIgnoreCase);

        }

​

        public void Index(string docId, string text) {

            var words = text.Split();

​

            string[] w;

            if (!_docIds.TryGetValue(docId, out w)) {

                _docIds.Add(docId, words);

            }

            else {

                _docIds[docId] = w;

                foreach (var t in w) {

                    _terms[t].Remove(docId);

                }

            }

​

​

            foreach (var term in words) {

                List<string> val;

                if (_terms.TryGetValue(term, out val) == false) {

                    val = new List<string>();

                    _terms[term] = val;

                }

                val.Add(docId);

            }

​

        }

​

        public List<string> Query(string term) {

            List<string> val;

            _terms.TryGetValue(term, out val);

            return val ?? new List<string>();

        }

​

        public void Delete(string docId) {

            throw new NotImplementedException();

        }

    }

​

    public class IndexTests {

        public static void CanIndexAndQuery() {

            var index = new CustomIndexer();

            index.Index("users/1", "Oren Eini");

            index.Index("users/3", "Oren Eini");

            index.Index("users/2", "Hibernating Rhinos");

​

            var b1 = index.Query("eini").Contains("users/1");

            var b2 = index.Query("rhinos").Contains("users/2");

​

            Console.WriteLine(b1 && b2);

        }

​

        public static void CanUpdate() {

            var index = new CustomIndexer();

            index.Index("users/1", "Oren Eini");

            index.Index("users/3", "Oren Eini");

            index.Index("users/2", "Hibernating Rhinos");

            //updating

            index.Index("users/1", "Ayende Rahien");

​

            var b1 = index.Query("Rahien").Contains("users/1");

            var b2 = index.Query("eini").Count() == 1;

            var b3 = index.Query("eini").Contains("users/3");

​

            Console.WriteLine(b1 && b2 && b3);

        }

​

        public static void CanDelete() {

            var index = new CustomIndexer();

            index.Index("users/1", "Oren Eini");

            index.Index("users/3", "Oren Eini");

            index.Index("users/2", "Hibernating Rhinos");

​

            index.Delete("users/1");

​

            var b1 = index.Query("Oren").Contains("users/3");

            var b2 = index.Query("eini").Count() == 1;

            var b3 = index.Query("Hibernating").Contains("users/2");

​

            Console.WriteLine(b1 && b2 && b3);

        }

    }