Isomorphic Strings | Leetcode

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.

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Solution: Maintain a two-way mapping (c1 <-> c2) between each character in the string in the same index. If we find that something was previous mapped but not matching the current characters in s and t, then the strings are not isomorphic. If we did not find any discrepancies, return true.

public class Solution {
    public boolean isIsomorphic(String s, String t) {
        if (s.length() != t.length()) return false;
        
        Map<Integer, Integer> map1 = new HashMap<>();
        Map<Integer, Integer> map2 = new HashMap<>();
        
        for (int i = 0; i < s.length(); i++) {
            int c1 = s.charAt(i);
            int c2 = t.charAt(i);
            
            Integer m1 = map1.get(c1);
            if (m1 != null && m1 != c2) return false;
            
            Integer m2 = map2.get(c2);
            if (m2 != null && m2 != c1) return false;
            
            map1.put(c1, c2);
            map2.put(c2, c1);
        }
        
        return true;
    }
}