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 

Credits:
Special thanks to @ifanchu for adding this problem and creating all test cases.

class Solution {
public:
    string convertToTitle(int n) 
    {
        string res="";
        if(n==0)
            return res;
        while(n>0)
        {
            int t = n%26;
            if(t==0)
            {
                res = res+(char)(90);
                n = n-26;
            }
            else
                res = res + (char)(t+64);
            n = n/26;
        }
        int m = res.length();
        int l = 0;
        int h = m-1;
        while(l<h)
            swap(res,l++,h--);
        return res;
    }
    void swap(string& s, int i, int j)
    {
        char t = s[i];
        s[i] = s[j];
        s[j] = t;
    }
    
};

LeetCode--Excel Sheet Column Title