【leetcode刷题笔记】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 

题解：其实就是一个26进制数转换成十进制数的程序：s[0]*26^(n-1)+s[1]*26^(n-2)+...+s[n-1]*26^(0)。计算的时候为了方便，从字符串最后一位开始计算，设置一个multi变量，初始值为1，每次多累加一位，就增加26倍。

Java代码如下：

 1 public class Solution {

 2     public int titleToNumber(String s) {

 3         int n = s.length();

 4         int multi = 1;

 5         int sum = 0;

 6         for(int i = n-1;i>=0;i--){

 7             sum += (s.charAt(i)-'A'+1)*multi;

 8             multi *= 26;

 9         }

10         return sum;

11     }

12 }