LeetCode171. Excel Sheet Column Number

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 
    ...

Example 1:

Input: "A"
Output: 1

Example 2:

Input: "AB"
Output: 28

Example 3:

Input: "ZY"
Output: 701

---

<思路>主要是熟悉ord的用法，返回ascii码代表的数值。思路上比较简单，注意A的ascii是65，所以这里需要减去64。

class Solution(object):
    def titleToNumber(self, s):
        """
        :type s: str
        :rtype: int
        """
        sum = 0
        for letter in s:
            num = ord(letter)-64
            sum = sum*26 + num
            
        return sum