IsomorphicStrings.java

// Time Complexity :O(n)
// Space Complexity :O(1)
// Did this code successfully run on Leetcode :Yes
// Any problem you faced while coding this :
class Solution {

    public boolean isIsomorphic(String s, String t) {
        int sLength = s.length();
        int tLength = t.length();
        if (sLength != tLength)
            return false;
        HashMap<Character, Character> sMap = new HashMap<Character, Character>();
        HashMap<Character, Character> tMap = new HashMap<Character, Character>();
        for (int i = 0; i < sLength; i++) {
            char sChar = s.charAt(i);
            char tChar = t.charAt(i);
            if (!sMap.containsKey(sChar)) {
                sMap.put(sChar, tChar);
            } else {
                if (sMap.get(sChar) != tChar) {
                    return false;
                }
            }

            if (!tMap.containsKey(tChar)) {
                tMap.put(tChar, sChar);
            } else {
                if (tMap.get(tChar) != sChar) {
                    return false;
                }
            }
        }
        return true;
    }
}