class Solution {
    public boolean isIsomorphic(String s, String t) {
        HashMap<Character, Character> mapS = new HashMap<>();
        HashMap<Character, Character> mapT = new HashMap<>();

        int s1=0, t1=0;

        while(s1 < s.length() && t1 < t.length()){
            if((mapS.containsKey(s.charAt(s1)) && mapS.get(s.charAt(s1)) != t.charAt(t1)) ||
            (mapT.containsKey(t.charAt(t1)) && mapT.get(t.charAt(t1)) != s.charAt(s1))){
                return false;
            }
            mapS.put(s.charAt(s1), t.charAt(t1));
            mapT.put(t.charAt(t1), s.charAt(s1));
            s1 += 1;
            t1 += 1;
        }
        return true;
    }
}