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171. Excel Sheet Column Number

 

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 


C++(6ms):
 1 class Solution {
 2 public:
 3     int titleToNumber(string s) {
 4         int ans = 0 ;
 5         int k = 0 ;
 6         for (int i = s.size()-1; i >= 0;i-- ){
 7             ans += (s[i]-A+1)*pow(26,k++);
 8         }
 9         return ans ;
10     }
11 };

 

C++(9ms):

 1 class Solution {
 2 public:
 3     int titleToNumber(string s) {
 4         int ans = 0 ;
 5         int k = 0 ;
 6         for (int i = 0; i < s.size();i++ ){
 7             ans = ans * 26 + (s[i]-A+1);
 8         }
 9         return ans ;
10     }
11 };

 

171. Excel Sheet Column Number