leetcode 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 

解題思路

26進制轉10進制
C = 3 = ‘C’-‘A’+1+26*0；
AA = 1+26=27=’A’-‘A’+1+26*1；
AB = 2+26=27 = ‘B’-‘A’+1+26*1；

代碼實現

public class Solution {
    public int titleToNumber(String s) {
         s = s.toUpperCase();
         char[] cs = s.toCharArray();
         int result=0;
         for(int i = 0 ; i < cs.length;i++){
             result = result*26+(cs[i]-'A'+1);
         }
         return result;
    }
}