13. Roman to Integer

Given a roman numeral, convert it to an integer.

Input is guaranteed to be within the range from 1 to 3999.

给定一个罗马数字，将其转换为整数。
保证输入在1到3999之间。

程序:

  public class RomanToIntSolution    {        //O(n) solution        public static int RomanToInt(string s)        {            var charArray = s.ToCharArray();            var sum = 0;            for (int i = 0; i < charArray.Length; i++)            {                if (charArray[i] == 'M')                    sum += 1000;                else if (charArray[i] == 'D')                    sum += 500;                else if (charArray[i] == 'C')                {                    if (i < charArray.Length - 1 && charArray[i + 1] == 'M')                    {                        sum += 900;                        i++;                    }                    else if (i < charArray.Length - 1 && charArray[i + 1] == 'D')                    {                        sum += 400;                        i++;                    }                    else sum += 100;                }                else if (charArray[i] == 'L')                    sum += 50;                else if (charArray[i] == 'X')                {                    if (i < charArray.Length - 1 && charArray[i + 1] == 'C')                    {                        sum += 90;                        i++;                    }                    else if (i < charArray.Length - 1 && charArray[i + 1] == 'L')                    {                        sum += 40;                        i++;                    }                    else sum += 10;                }                else if (charArray[i] == 'V')                    sum += 5;                else if (charArray[i] == 'I')                {                    if (i < charArray.Length - 1 && charArray[i + 1] == 'X')                    {                        sum += 9;                        i++;                    }                    else if (i < charArray.Length - 1 && charArray[i + 1] == 'V')                    {                        sum += 4;                        i++;                    }                    else sum += 1;                }            }            return sum;        }    }

单元测试(通过):

  [TestClass]    public class UnitTest13_RomanToInteger    {        [TestMethod]        public void TestMethodRomanToInt()        {            var list = new Dictionary<int, string>();            list[1] = "I";            list[2] = "II";            list[3] = "III";            list[4] = "IV";            list[5] = "V";            list[6] = "VI";            list[7] = "VII";            list[8] = "VIII";            list[9] = "IX";            list[10] = "X";            list[14] = "XIV";            list[19] = "XIX";            list[20] = "XX";            list[49] = "XLIX";            list[50] = "L";            list[99] = "XCIX";            list[100] = "C";            list[499] = "CDXCIX";            list[500] = "D";            list[999] = "CMXCIX";            list[1000] = "M";            list[3999] = "MMMCMXCIX";            foreach (var pair in list)                Assert.AreEqual(pair.Key, RomanToIntSolution.RomanToInt(pair.Value));        }    }