## 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;


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