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 
...

Example 1:

Input: 1 Output: "A" Example 2:

Input: 28 Output: "AB" Example 3:

Input: 701 Output: "ZY"

Solution:

The tricky part is how to handle 26 and 27.

string convertToTitle(int n) {
    string res;
    while (n) {
        n -= 1;
        res += n % 26 + 'A';
        n /= 26;
    }
    return string(res.rbegin(), res.rend());
}