[leetcode] Excel Sheet Column Title

From : https://leetcode.com/problems/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

class Solution {
public:
string convertToTitle(int n) {
string res = "";
char c;
int base = 26;
while(n>0) {
c = 'A' + (n%base + 25)%26;
res = c + res;
n = (n%26?n/26:n/26-1);
}
return res;
}
};