【leetcode❤python】171. Excel Sheet Column Number

#-*- coding: UTF-8 -*-
# ord(c) -> integer
##Return the integer ordinal of a one-character string.
##参数是一个ascii字符，返回值是对应的十进制整数
class Solution(object):
    def titleToNumber(self, s):
        columns=0
        n=len(s)
        s=s.upper()[::-1]
        for c in range(len(s)):
          
            columns+=(ord(s[c])-64)*pow(26,c)
     
        return columns

sol=Solution()
print sol.titleToNumber('a')