leetcode168

public class Solution {
    private string Convert(int k)
        {
            var s = "";
            switch (k)
            {
                case :
                    s = "A";
                    break;
                case :
                    s = "B";
                    break;
                case :
                    s = "C";
                    break;
                case :
                    s = "D";
                    break;
                case :
                    s = "E";
                    break;
                case :
                    s = "F";
                    break;
                case :
                    s = "G";
                    break;
                case :
                    s = "H";
                    break;
                case :
                    s = "I";
                    break;
                case :
                    s = "J";
                    break;
                case :
                    s = "K";
                    break;
                case :
                    s = "L";
                    break;
                case :
                    s = "M";
                    break;
                case :
                    s = "N";
                    break;
                case :
                    s = "O";
                    break;
                case :
                    s = "P";
                    break;
                case :
                    s = "Q";
                    break;
                case :
                    s = "R";
                    break;
                case :
                    s = "S";
                    break;
                case :
                    s = "T";
                    break;
                case :
                    s = "U";
                    break;
                case :
                    s = "V";
                    break;
                case :
                    s = "W";
                    break;
                case :
                    s = "X";
                    break;
                case :
                    s = "Y";
                    break;
                case :
                    s = "Z";
                    break;
            }
            return s;
        }

        public string ConvertToTitle(int n)
        {
            var list = new List<int>();
            while (n != )
            {
                var k = n % ;
                list.Add(k);
                if (k == )
                {
                    n = n /  - ;
                }
                else
                {
                    n = n / ;
                }
            }

            list.Reverse();

            StringBuilder sb = new StringBuilder();
            for (int i = ; i < list.Count; i++)
            {
                var s = Convert(list[i]);
                sb.Append(s);
            }
            return sb.ToString();
        }
}

https://leetcode.com/problems/excel-sheet-column-title/#/description