LeetCode Excel Sheet Column Number JAVA

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 

写的比较挫，先是判断一下，如果是String只有一个单词的话，就比较简单，直接返回这个单词对应的值就行了。如果有多个单词的话，就先把第一个到倒数第二个的所有和都加起来，再加上最后一位的值就OK了。

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