171. Excel Sheet Column Number Leetcode Python

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.

这题可以当作求26进制数来做。 可以用iterative的方法也可以用递归的方法来做

iterative:

class Solution:
    # @param s, a string
    # @return an integer
    def titleToNumber(self, s):
        result=0
        n=len(s)
        for i in range(n):
            result=result*26+ord(s[i])-64
        return result

recursive:

class Solution:
    # @param s, a string
    # @return an integer
    def titleToNumber(self, s):
        if len(s)==1:
            return ord(s)-64
        return ord(s[-1])-64+26*self.titleToNumber(s[:-1])

总体来说第一种方法速度比第二种要快。