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.

public class Solution {
    public String convertToTitle(int n) {
        //if n<=0 return empty string;
        StringBuilder sb = new StringBuilder();
       
        while(n>0) {
            int x = n % 26;
            if(x == 0) {
                sb.append('Z');
                --n;
            } else {
                sb.append((char)('A'-1+x));
            }
            n /= 26;
        }
        return sb.reverse().toString();
    }
}

leetcode 154: Excel Sheet Column Title