Isomorphic Strings

Given two strings s and t, determine if they are isomorphic.

Two strings are isomorphic if the characters in s can be replaced to get t.

All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character but a character may map to itself.

For example,

Given “egg”, “add”, return true.

Given “foo”, “bar”, return false.

Given “paper”, “title”, return true.

Note:

You may assume both s and t have the same length.

Solution:

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