namespace Interview_Other

{

    using System;

    using System.Collections.Generic;

    using System.Linq;

​

    public class Program

    {

        public enum StringConversion

        {

            None,

            Swap,

            Insert,

            Delete,

            Unknown,

        };

​

        public static void Main(string[] args)

        {

            Dictionary<Tuple<string, string>, StringConversion> tests = new Dictionary<Tuple<string, string>, StringConversion>{

                {new Tuple<string,string>("command","command"), StringConversion.None},

​

                 {new Tuple<string,string>("ommand", "xommand"), StringConversion.Insert},

                 {new Tuple<string,string>("comman", "commanx"), StringConversion.Insert},

​

                  {new Tuple<string,string>("xommand", "ommand"),StringConversion.Delete},

                  {new Tuple<string,string>("commanx", "comman"),StringConversion.Delete},

​

                  {new Tuple<string,string>("command", "comxand"),StringConversion.Swap},

                  {new Tuple<string,string>("command", "xommand"),StringConversion.Swap},

                  {new Tuple<string,string>("command", "commanx"),StringConversion.Swap},

​

                  {new Tuple<string,string>("command", "xxmmand"),StringConversion.Unknown},

                  {new Tuple<string,string>("command", "dommanc"),StringConversion.Unknown},

​

            };

​

​

            tests.ToList().ForEach(kvp => {

                var result = Compare(kvp.Key.Item1, kvp.Key.Item2);

                var success = result == kvp.Value ? "Success" : "Failure";

                Console.WriteLine(success + ": ("+kvp.Key.Item1 +"," + kvp.Key.Item2+") => "+result+" - expected "+kvp.Value+"");

            });

        }

​

        public static StringConversion Compare(string a, string b)

        {

​

            var conversionType = StringConversion.Unknown;

            var differences = 0;

​

            // true if strings are 1 char different

            // whether add/subtract or 1 char swapped out

            if (a == b)

            {

                conversionType = StringConversion.None;

            }

            else if (a.Length == b.Length)

            {

                conversionType = StringConversion.Swap;

                differences = CheckInsertDeleteSwap(a, b, conversionType);

            }

            else if (a.Length + 1 == b.Length)

            {

                conversionType = StringConversion.Insert;

                differences = CheckInsertDeleteSwap(a, b);

            }

            else if (a.Length == b.Length + 1)

            {

                conversionType = StringConversion.Delete;

                differences = CheckInsertDeleteSwap(b, a);

            }

​

            if (differences <= 1)

            {

                return conversionType;

            }

            return StringConversion.Unknown;

        }

​

        static int CheckInsertDeleteSwap(string small, string big, StringConversion conversionType = 0)

        {

            var differences = 0;

            for (int i = 0; i < small.Length; i++)

            {

                //if out of bounds or already found a difference

                if (differences > 1 || small.Length <= i)

                    break;

​

                if (small[i] == big[i])

                    continue;

​

                // they are not the same character. remove the char from the 'big' string

                big = big.Remove(i, 1);

​

                // if we expected a swap, remove the character from the small string too

                if (conversionType == StringConversion.Swap)

                    small = small.Remove(i, 1);

​

                i--;

                differences++;

            }

​

            return differences;

        }

    }

}

​