168. 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

The solution

1. turn 1-based col number to 0-based in each round.
2. get the aplabetic representation from left to right, by using mod operation.
3. reduce the number using / operation. disgard the remainder. use quotient for next round.

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

    }
}