leetcode 171. Excel Sheet Column Number

Seawolf

1. Given a column title as appear in an Excel sheet, return its corresponding column number.
   
2. 
   
3. For example:
   
4. 
   
5.     A -> 1
   
6.     B -> 2
   
7.     C -> 3
   
8.     ...
   
9.     Z -> 26
   
10.     AA -> 27
    
11.     AB -> 28
    
12.     ...
    
13. Example 1:
    
14. 
    
15. Input: "A"
    
16. Output: 1
    
17. Example 2:
    
18. 
    
19. Input: "AB"
    
20. Output: 28
    
21. Example 3:
    
22. 
    
23. Input: "ZY"
    
24. Output: 701

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1. class Solution {
   
2.     public int titleToNumber(String s) {
   
3.         if(s.length() == 0) return 0;
   
4.         
   
5.         if(s.length()>1)
   
6.             return (s.charAt(0) - 'A'+1)*((int)Math.pow(26,s.length() - 1)) + titleToNumber(s.substring(1));
   
7.         else return (s.charAt(0) - 'A'+1)*((int)Math.pow(26,s.length() - 1));
   
8.     }
   
9. }

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