LeetCode 171 Excel Sheet Column Number

Problem:

Given a column title as appear in an Excel sheet, return its corresponding column number.

For example:

    A -> 1
    B -> 2
    C -> 3
    ...
    Z -> 26
    AA -> 27
    AB -> 28 

Summary:

将二十六进制数字转为十进制。

Analysis:

 class Solution {
 public:
     int titleToNumber(string s) {
         int len = s.size();
         int res = ;

         for (int i = ; i < len; i++) {
             res += (s[len - i - ] - 'A' + ) * pow(, i);
         }

         return res;
     }
 };