題目

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 
    ...

Example 1:

Input: "A"
Output: 1

Example 2:

Input: "AB"
Output: 28

Example 3:

Input: "ZY"
Output: 701

解法

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

比如ABC  

0*26+1=1    1*26+2=28   28*26+3=731

再比如AB

0*26+1=1  1*26+2=28