737.Sentence Similarity II

class Solution {
    public boolean areSentencesSimilarTwo(String[] words1, String[] words2, String[][] pairs) {
        if(words1.length != words2.length)
            return false;

        Map<String, String> roots = new HashMap<>();
        for(String[] pair : pairs){
            roots.put(pair[0], pair[0]);
            roots.put(pair[1], pair[1]);
        }

        for(String[] pair : pairs){
            String root1 = find(roots, pair[0]);
            String root2 = find(roots, pair[1]);
            if(!root1.equals(root2)){
                roots.put(root1, root2);
            }
        }

        for(int i = 0; i < words1.length; i++){
            if(words1[i].equals(words2[i]))
                continue;
            String root1 = find(roots, words1[i]);
            String root2 = find(roots, words2[i]);
            if(root1 == null || root2 == null)
                return false;
            if(!root1.equals(root2))
                return false;
        }
        return true;

    }
    public String find(Map<String, String> roots, String word){
        if(!roots.containsKey(word)){
            return null;
        }
        else if(roots.get(word).equals(word)){
            return word;
        }
        else
            return find(roots, roots.get(word));
    }
}