171. Excel Sheet Column Number

problem

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.

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solution

• 类似二十六进制转换成十进制
• 使用ord chr进行ascii转换

class Solution(object):
    def titleToNumber(self, s):
        """
        :type s: str
        :rtype: int
        """
        product = len(s)-1
        num = 0
        for x in s:
            num += (ord(x)-64)*26**product
            product -= 1
        return num

discuss

一些更短小的写法，逻辑一样

return reduce(lambda x, y : x * 26 + y, [ord(c) - 64 for c in list(s)])

return reduce(lambda x,y:x*26+y,map(lambda x:ord(x)-ord('A')+1,s))

return reduce(lambda x, y: 26*x+ord(y)-64, s, 0)