1271. Hexspeak

A decimal number can be converted to its Hexspeak representation by first converting it to an uppercase hexadecimal string, then replacing all occurrences of the digit 0 with the letter O, and the digit 1 with the letter I.  Such a representation is valid if and only if it consists only of the letters in the set {"A", "B", "C", "D", "E", "F", "I", "O"}.

Given a string num representing a decimal integer N, return the Hexspeak representation of N if it is valid, otherwise return "ERROR".

Example 1:

Input: num = "257"
Output: "IOI"
Explanation:  257 is 101 in hexadecimal.

Example 2:

Input: num = "3"
Output: "ERROR"

Constraints:

• 1 <= N <= 10^12
• There are no leading zeros in the given string.
• All answers must be in uppercase letters.

class Solution {
   public String toHexspeak(String num) {
        long n = Long.parseLong(num);
        String res = Long.toHexString(n).toUpperCase().replace('1', 'I').replace('0', 'O');
        for (char c : res.toCharArray())
            if (Character.isDigit(c))
                return "ERROR";
        return res;        
    }
}

class Solution {
    public String toHexspeak(String num) {
        
        long n = Long.parseLong(num);
        HashMap<Integer, Character> map = new HashMap<>();
        map.put(0, 'O');
        map.put(1, 'I');
        map.put(10, 'A');
        map.put(11, 'B');
        map.put(12, 'C');
        map.put(13, 'D');
        map.put(14, 'E');
        map.put(15, 'F');
        
        String ans = "";
        
        while(n > 0){
            int rem = (int)(n % 16);
            if(rem > 1 && rem < 10) return "ERROR";
            n = n / 16;
            ans = map.get(rem) + ans;
        }
        
        return ans;
        
    }
}