leetcode Question: Excel Sheet Column Title

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 

Analysis:

This problem is not difficult but needs more attention on the format.
General cases are straightforward:
27 -> AA                 27/26 = 1,  27%26 = 1,     1->A, 1->A   thus AA
3  ->  C                    3/26 = 0,    3%26 = C        0->   , 3->C   thus C
53 -> BA                 53/26 = 2,   53%26 = 1      2->B, 1->A   thus BA

Some special cases we need to handle:
26 -> Z                    26/26 = 0,  26%26 = 0
52 -> AZ                 26/26 = 2,   26%26 = 0

When n%26 == 0, the last digit must be filled with a 'Z', therefore n in the next step must subtract this 'Z' (which is 26) and continue.

Code(C++):

class Solution {
public:
    string convertToTitle(int n) {
        string res = "";
        while (n>0){
            if (n%26==0){
                res = 'Z' + res;
                n = n/26 -1;
            }else{
                res = char(n%26 -1 + 'A') + res;
                n = n/26;
            }
        }
        return res;
    }
};

Code(Python):

class Solution:
    # @param {integer} n
    # @return {string}
    def convertToTitle(self, n):
        res = ''
        while n > 0:
            if n%26 == 0:
                res = 'Z' + res
                n = n/26 -1
            else:
                res = chr(ord('A') + n%26 - 1) + res
                n = n/26
        return res;