737. Sentence Similarity II

class Solution {
    public boolean areSentencesSimilarTwo(String[] words1, String[] words2, String[][] pairs) {
        int m = words1.length, n = words2.length;
        if(m != n) return false;
        Map<String, String> map = new HashMap<>();
        for(String[] pair : pairs)
        {
            String u = pair[0], v = pair[1];
            if(!map.containsKey(u)) map.put(u, u);
            if(!map.containsKey(v)) map.put(v, v);
            String pu = parent(u, map), pv = parent(v, map);
            if(!pu.equals(pv)) map.put(pu, pv);
        }
        for(int i = 0; i < m; i++)
        {
            String u = words1[i], v = words2[i], pu = parent(u, map), pv = parent(v, map);
            if(u.equals(v) || (pu != null && pv != null && pu.equals(pv))) continue;
            if(pu == null || pv == null) return false;
            return false;
        }
        return true;
    }

    String parent(String str, Map<String, String> map)
    {
        if(!map.containsKey(str)) return null;
        String p = map.get(str);
        while(!p.equals(map.get(p))) p = map.get(p);
        map.put(str, p);
        return p;
    }
}