Excel Sheet Column Title

Given a positive integer, return its corresponding column title as appear in an Excel sheet.

For example:

    1 -> A
    2 -> B
    3 -> C
    ...
    26 -> Z
    27 -> AA
    28 -> AB

n - 1 很重要，可以用26作为例子思考一下

Recursion

class Solution(object):
    def convertToTitle(self, n):
        """
        :type n: int
        :rtype: str
        """
        if n == 0:
            return ""
        return self.convertToTitle((n - 1) / 26) + chr((n - 1) % 26 + ord('A'))

Iteration

class Solution(object):
    def convertToTitle(self, n):
        """
        :type n: int
        :rtype: str
        """
        res = ''
        while n:
            res = chr((n - 1) % 26 + ord('A')) + res
            n = (n - 1) / 26
        return res