leetcode171

public class Solution {
    private int ConvertToC(char c)
        {
            int rnt = 0;

            switch (c)
            {
                case 'A':
                case 'a':
                    rnt = 1;
                    break;
                case 'B':
                case 'b':
                    rnt = 2;
                    break;
                case 'C':
                case 'c':
                    rnt = 3;
                    break;
                case 'D':
                case 'd':
                    rnt = 4;
                    break;
                case 'E':
                case 'e':
                    rnt = 5;
                    break;
                case 'F':
                case 'f':
                    rnt = 6;
                    break;
                case 'G':
                case 'g':
                    rnt = 7;
                    break;
                case 'H':
                case 'h':
                    rnt = 8;
                    break;
                case 'I':
                case 'i':
                    rnt = 9;
                    break;
                case 'J':
                case 'j':
                    rnt = 10;
                    break;
                case 'K':
                case 'k':
                    rnt = 11;
                    break;
                case 'L':
                case 'l':
                    rnt = 12;
                    break;
                case 'M':
                case 'm':
                    rnt = 13;
                    break;
                case 'N':
                case 'n':
                    rnt = 14;
                    break;
                case 'O':
                case 'o':
                    rnt = 15;
                    break;
                case 'P':
                case 'p':
                    rnt = 16;
                    break;
                case 'Q':
                case 'q':
                    rnt = 17;
                    break;
                case 'R':
                case 'r':
                    rnt = 18;
                    break;
                case 'S':
                case 's':
                    rnt = 19;
                    break;
                case 'T':
                case 't':
                    rnt = 20;
                    break;
                case 'U':
                case 'u':
                    rnt = 21;
                    break;
                case 'V':
                case 'v':
                    rnt = 22;
                    break;
                case 'W':
                case 'w':
                    rnt = 23;
                    break;
                case 'X':
                case 'x':
                    rnt = 24;
                    break;
                case 'Y':
                case 'y':
                    rnt = 25;
                    break;
                case 'Z':
                case 'z':
                    rnt = 26;
                    break;
                default:
                    rnt = 0;
                    break;
            }
            return rnt;
        }

        public int TitleToNumber(string s)
        {
            var list = s.ToList();
            var count = list.Count;
            
            int sum = 0;

            for (int i = 0; i < list.Count; i++)
            {
                var mi = count - i - 1;
                //mi是幂  * pow(26,mi)
                int num = ConvertToC(list[i]);
                sum += num * Convert.ToInt32(Math.Pow(26, mi));
            }

            Console.WriteLine(sum);
            return sum;
        }
}

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

补充一个python的实现：

class Solution:
    def titleToNumber(self, s: 'str') -> 'int':
        s = s.upper()
        n = len(s)
        sums = 0
        k = 0
        for i in range(n-1,-1,-1):
            asci = ord(s[i]) - 64
            sums += 26 ** k * asci
            k += 1
        return sums