Merging Details.java

class Solution {
    public int[] par;

    public List<List<String>> mergeDetails(List<List<String>> details) {
        par = new int[details.size()];
        for(int i = 0; i < par.length; i++)
            par[i] = i;
        HashMap<String, Integer> map = new HashMap<>();
        for(int i = 0; i < details.size(); i++){
            for(int j = 1; j < details.get(i).size(); j++){
            	String email = details.get(i).get(j);
                if(map.containsKey(email)) {
                	int fir = i;
                	int sec = map.get(email);
                	merge(fir, sec);
                }
                map.put(email, i);
            }
        }
        HashMap<Integer, Integer> pos = new HashMap<>();
        List<List<String>> ans = new ArrayList<>();
        for(int i = 0; i < par.length; i++) {
        	int val = find(i);
        	int newnum = -1;
        	if(pos.containsKey(val))
        		newnum = pos.get(val);
        	else {
        		newnum = ans.size();
        		ans.add(new ArrayList<>());
        	}
        	for(int j = 1; j < details.get(i).size(); j++) {
        		String email = details.get(i).get(j);
        		if(ans.get(newnum).contains(email) == false)
        			ans.get(newnum).add(email);
        	}
        	pos.put(val, newnum);
        }
        for(List<String> ls : ans)
        	Collections.sort(ls);
        for(int i = 0; i < par.length; i++) {
        	if(pos.containsKey(find(i))) {
        		ans.get(pos.get(par[i])).add(0, details.get(i).get(0));
        		pos.remove(par[i]);
        	}
        }
        return ans;
    }
    
    public int find(int x) {
    	if(par[x] == x)
    		return x;
    	return par[x] = find(par[x]);
    }
    
    public void merge(int fir, int sec) {
    	par[fir] = sec;
    }
}