LeetCode: Excel Sheet Column Title

Question:

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

Thoughts:

Covert decimal number to 26th numeral system number.

Key point need to consider:

• If given number is a a multiple of 26, then
  • modResult = modResult + 1
  • quotient = quotient – 1

public class Solution {
    public String convertToTitle(int n) {
        //remove edge case
        if (n < 1) {
            return "";
        }
        
        //use a string buffer to build final result
        StringBuffer sb = new StringBuffer();
        while (n != 0) {
            int digit = n % 26;
            n = n / 26;
            
            //key point need to consider
            if (digit == 0) {
                digit = 26;
                n -= 1;
            }
            
            digit -= 1;
            char c = (char) (digit + 'A');
            sb.append(c);
        }
        
        //because StringBuffer is built in reverse order
        //so reverse it to correct order
        sb.reverse();
        return new String(sb);
    }
}