171. Excel表列序號

題目其實就是轉換26進位制， $26^n\ast m_n+$

class Solution {
    public int titleToNumber(String s) {
        char[] ss = s.toCharArray();
        int n = ss.length-1;
        int square;
        int total = 0;
        
        for(int i=0; i<ss.length; i++){
            square = (int)Math.pow(26, n);
            n--;
            total += ((int)ss[i]-64)*square;
        }
        return total;    
    }
}