LeetCode Problem #168 : Excel Sheet Column Title

Question:

Given an integer columnNumber, return its corresponding column title as it appears in an Excel sheet.

For example:

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

Example 1:

Input: columnNumber = 1
Output: "A"
Example 2:

Input: columnNumber = 28
Output: "AB"
Example 3:

Input: columnNumber = 701
Output: "ZY"

Constraints:

1 <= prices.length <= 10⁵
0 <= prices[i] <= 10⁴

Initial Solution:

I almost got this answer by itself, but for the fact that we need to subtract one from every iteration so as to comply with the conversion rule. nice trick...

    class Solution {
    public String convertToTitle(int columnNumber) {
        String answer = "";
        HashMap<Integer,String> map = new HashMap<>();
        map.put(0,"A");
        map.put(1,"B");
        map.put(2,"C");
        map.put(3,"D");
        map.put(4,"E");
        map.put(5,"F");
        map.put(6,"G");
        map.put(7,"H");
        map.put(8,"I");
        map.put(9,"J");
        map.put(10,"K");
        map.put(11,"L");
        map.put(12,"M");
        map.put(13,"N");
        map.put(14,"O");
        map.put(15,"P");
        map.put(16,"Q");
        map.put(17,"R");
        map.put(18,"S");
        map.put(19,"T");
        map.put(20,"U");
        map.put(21,"V");
        map.put(22,"W");
        map.put(23,"X");
        map.put(24,"Y");
        map.put(25,"Z");
        while(columnNumber > 0){
            columnNumber--;
            answer = map.get(columnNumber%26) + answer;
            columnNumber /= 26;
        }
        return answer;
    }
}

Peformance:

N/A