168. Excel表列名称

    1 -> A
    2 -> B
    3 -> C
    ...
    26 -> Z
    27 -> AA
    28 -> AB 
    ...

输入: 1
输出: "A"

输入: 28
输出: "AB"

输入: 701
输出: "ZY"

class Solution {
    public String convertToTitle(int n) {
        char a = 'A';
        StringBuilder sb = new StringBuilder();
        while (n != 0) {
            a = 'A';
            a += (n - 1) % 26;
            sb.append(a);
            n = (n - 1) / 26;
        }
        sb.reverse();
        return sb.toString();
    }
}