leetcode----------Excel Sheet Column Number

題目	Excel Sheet Column Number
經過率	40.5%
難度	Easy

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 


題目分析：處理26進制，逐個讀入字符串的每個字符進行處理轉換，逐個移位；

java代碼：

public class Solution {
    public int titleToNumber(String s) {
        int i=0;
        int num=0;
        while(i<s.length()){
            if(s.charAt(i)!='Z'){
                num=num*26+s.charAt(i)-65+1;
            }
            else num=num*26+26;
            i++;
        }
        return num;
    }
}