leetcode_Excel Sheet Column Number

171. Excel Sheet Column Number

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 

如题，题目可理解为二十六进制的转化。

代码如下：

public class Solution {    public int titleToNumber(String s) {        int num=0;int[] a =new int[s.length()];for(int j = 0; j < s.length(); j++){a[j]=s.charAt(j)-'A'+1;num=num+Pow(26,s.length()-j-1)*a[j];}return num;    }    private static int Pow(int i, int j){if(j==0) return 1;return i*Pow(i,j-1);}}

或是比较灵巧的方法：如下：
public class Solution {    public int titleToNumber(String s) {        int num=0;for(int j = 0; j < s.length(); j++){num=num*26+s.charAt(j)-"A"+1;}return num;    }  }