56. Merge Intervals

class Solution {
    public List<Interval> merge(List<Interval> intervals) {
        List<Interval> res=new ArrayList<Interval>();
        if(intervals.size()==0)
            return res;
        Collections.sort(intervals, (a,b)->a.start-b.start);
        int start=0;
        int end=0;
        for(int i=0;i<intervals.size();i++)
        {
            if(i==0)
            {
                start=intervals.get(i).start;
                end=intervals.get(i).end;
            }
            else if(end<intervals.get(i).start)
            {
                res.add(new Interval(start,end));
                start=intervals.get(i).start;
                end=intervals.get(i).end;
            }
            else
                end=Math.max(end, intervals.get(i).end);
        }
        res.add(new Interval(start,end));
        return res;
    }
}