LeetCode - Merge Intervals

Merge Intervals

//
public List<Interval> merge(List<Interval> intervals) {
        ArrayList<Interval> ret = new ArrayList<Interval>();
        if(intervals == null || intervals.size() ==0) return ret;
        Collections.sort(intervals, comparator);
        Interval newInterval = intervals.get(0);
        for(int i=1; i<intervals.size(); i++){
            Interval curInterval = intervals.get(i);
            if(curInterval.start > newInterval.end){
                ret.add(newInterval);
                newInterval = curInterval;
            } else if (curInterval.end < newInterval.start){
                ret.add(curInterval);
            } else {
                newInterval = new Interval(Math.min(newInterval.start, curInterval.start), Math.max(newInterval.end, curInterval.end));
            }
        }
        ret.add(newInterval);
        return ret;
    }
    
    public Comparator<Interval> comparator = new Comparator<Interval>(){
      @Override
      public int compare(Interval interval1, Interval interval2){
          return interval1.start - interval2.start;
      }
    };
// better solution 
public ArrayList<Interval> merge(ArrayList<Interval> intervals) {
        ArrayList<Interval> ret = new ArrayList<Interval>();
        if(intervals==null || intervals.size()==0){
            return intervals;
        }
        Comparator<Interval> comp = new Comparator<Interval>(){
            public int compare(Interval i1, Interval i2){
                if(i1.start==i2.start)
                    return i1.end-i2.end;
                return i1.start-i2.start;
            }
        };
        Collections.sort(intervals, comp);
        ret.add(intervals.get(0));
        for(int i=1; i<intervals.size(); i++){
            int index = ret.size()-1;
            if(ret.get(index).end>=intervals.get(i).start){
                ret.get(index).end = Math.max(intervals.get(i).end, ret.get(index).end);
            }else{
                ret.add(intervals.get(i));
            }
        }
        return ret;
    }