Merge Intervals

1. Title

Merge Intervals

2. Http address

https://leetcode.com/problems/merge-intervals/

3. The question

Given a collection of intervals, merge all overlapping intervals.

For example,
Given [1,3],[2,6],[8,10],[15,18],
return [1,6],[8,10],[15,18].

4 My code(AC)

•  

  // Accepted
        public static List<Interval> merge(List<Interval> intervals) {
           
            List<Interval> res = new ArrayList<Interval>();
            if ( intervals == null || intervals.isEmpty() )
                return res;
            
            Comparator<Interval> com = new Comparator<Interval>(){
                    public int compare(Interval a ,Interval b)
                    {
                        if ( a.start < b.start) return -1;
                        else if ( a.start > b.start ) return 1;
                        else {
                            if ( a.end < b.end) return -1;
                            else if ( a.end > b.end ) return 1;
                            else return 0;
                        }
                    }
            };
            
            Collections.sort(intervals,com);
            
            for( int i = 0 ; i < intervals.size(); i++)
            {
                Interval cur = intervals.get(i);
                if ( res.isEmpty() )
                {
                    res.add(cur);
                }else{
                    Interval last = res.get(res.size() - 1);
                    if ( last.end >= cur.start)
                    {
                        last.end = Math.max(last.end, cur.end);
                    }else{
                        res.add(cur);
                    }
                }
            }
            return res;
          }