30.leetcode171_excel_sheet_column_number

1.题目描述

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 

Credits:
Special thanks to @ts for adding this problem and creating all test cases.

26进制转10进制

2.题目分析

从字符串末尾开始遍历，依次加数

3.解题思路

class Solution(object):
    def titleToNumber(self, s):
        """
        :type s: str
        :rtype: int
        """
        l=len(s)
        i=l-1
        temp=ord('A')-1
        n=0
        while i>=0:
            n+=26**(l-i-1)*(ord(s[i])-temp)
            i-=1
        return n