Related to question Excel Sheet Column Title

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 

Credits:
Special thanks to @ts for adding this problem and creating all test cases.

解答

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