class Solution {

    public boolean isStrobogrammatic(String num) {

        Map<Character, Character> mymap = new HashMap<>();

        mymap.put('1', '1');

        mymap.put('8', '8');

        mymap.put('0', '0');

        mymap.put('6', '9');

        mymap.put('9', '6');

        int left = 0;

        int right = num.length() - 1;

        while (left <= right) {

            char left_char = num.charAt(left);

            char right_char = num.charAt(right);

            if (!mymap.containsKey(left_char) || !mymap.containsKey(right_char)) {

                return false;

            } else if (mymap.get(left_char) != right_char) {

                return false;

            }

            left += 1;

            right -= 1;

        }

        return true;

    }

}