class Solution {
    public boolean isIsomorphic(String s, String t) {
        Map<Character, Character> map = new HashMap<>();
        Map<Character, Character> map1 = new HashMap<>();
        for(int i=0; i<s.length(); i++){
            if(map.containsKey(s.charAt(i)) && map.get(s.charAt(i))!=t.charAt(i)
              || map1.containsKey(t.charAt(i)) && map1.get(t.charAt(i))!=s.charAt(i)){
                return false;
            }else if(!map.containsKey(s.charAt(i))){
                map.put(s.charAt(i), t.charAt(i));
                map1.put(t.charAt(i), s.charAt(i));
            }
        }
        return true;
    }
}