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)

 1 // Accepted
 2       public static List<Interval> merge(List<Interval> intervals) {
 3          
 4           List<Interval> res = new ArrayList<Interval>();
 5           if ( intervals == null || intervals.isEmpty() )
 6               return res;
 7           
 8           Comparator<Interval> com = new Comparator<Interval>(){
 9                   public int compare(Interval a ,Interval b)
10                   {
11                       if ( a.start < b.start) return -1;
12                       else if ( a.start > b.start ) return 1;
13                       else {
14                           if ( a.end < b.end) return -1;
15                           else if ( a.end > b.end ) return 1;
16                           else return 0;
17                       }
18                   }
19           };
20           
21           Collections.sort(intervals,com);
22           
23           for( int i = 0 ; i < intervals.size(); i++)
24           {
25               Interval cur = intervals.get(i);
26               if ( res.isEmpty() )
27               {
28                   res.add(cur);
29               }else{
30                   Interval last = res.get(res.size() - 1);
31                   if ( last.end >= cur.start)
32                   {
33                       last.end = Math.max(last.end, cur.end);
34                   }else{
35                       res.add(cur);
36                   }
37               }
38           }
39           return res;
40         }
41