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.

這題可以當作求26進位制數來做。 可以用iterative的方法也可以用遞迴的方法來做

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])
 

總體來說第一種方法速度比第二種要快。