Given a data stream input of non-negative integers a1, a2, ..., an, ..., summarize the numbers seen so far as a list of disjoint intervals.

For example, suppose the integers from the data stream are 1, 3, 7, 2, 6, ..., then the summary will be:

[1, 1]
[1, 1], [3, 3]
[1, 1], [3, 3], [7, 7]
[1, 3], [7, 7]
[1, 3], [6, 7]
Follow up:
What if there are lots of merges and the number of disjoint intervals are small compared to the data stream‘s size?

 1 /**
 2  * Definition for an interval.
 3  * public class Interval {
 4  *     int start;
 5  *     int end;
 6  *     Interval() { start = 0; end = 0; }
 7  *     Interval(int s, int e) { start = s; end = e; }
 8  * }
 9  */
10 public class SummaryRanges {
11     TreeMap<Integer, Interval> tree;
12 
13     /** Initialize your data structure here. */
14     public SummaryRanges() {
15         tree = new TreeMap<>();
16     }
17     
18     public void addNum(int val) {
19         if (tree.containsKey(val)) return;
20         Integer l = tree.lowerKey(val);
21         Integer h = tree.higherKey(val);
22         
23         //case 1: val is the only number between the two intervals
24         if (l!=null && h!=null && val==tree.get(l).end+1 && val==h-1) {
25             tree.get(l).end = tree.get(h).end;
26             tree.remove(h);
27         }
28         
29         //case 2 & 3: val is in one interval or is the next elem of that interval‘s last elem
30         else if (l!=null && val<=tree.get(l).end+1) {
31             tree.get(l).end = Math.max(tree.get(l).end, val);
32         }
33         
34         //case 4: val is the first elem of a interval
35         else if (h!=null && val==h-1) {
36             tree.put(val, new Interval(val, tree.get(h).end));
37             tree.remove(h);
38         }
39         
40         //case 5: val does not adhere to any interval
41         else {
42             tree.put(val, new Interval(val, val));
43         }
44     }
45     
46     public List<Interval> getIntervals() {
47         return new ArrayList<>(tree.values());
48     }
49 }
50 
51 /**
52  * Your SummaryRanges object will be instantiated and called as such:
53  * SummaryRanges obj = new SummaryRanges();
54  * obj.addNum(val);
55  * List<Interval> param_2 = obj.getIntervals();
56  */

 1 /**
 2  * Definition for an interval.
 3  * public class Interval {
 4  *     int start;
 5  *     int end;
 6  *     Interval() { start = 0; end = 0; }
 7  *     Interval(int s, int e) { start = s; end = e; }
 8  * }
 9  */
10 public class SummaryRanges {
11 
12     /** Initialize your data structure here. */
13     public SummaryRanges() {
14         itvlSet = new TreeSet<Interval>(new Comparator<Interval>(){
15             public int compare(Interval v1, Interval v2){
16                 return v1.start-v2.start;
17             }
18         });
19         
20     }
21     
22     public void addNum(int val) {
23         Interval itvl = new Interval(val,val);
24         Interval pre = itvlSet.floor(itvl);
25         Interval after = itvlSet.ceiling(itvl);
26         
27         if ( (pre!=null && pre.end >= val) || (after!=null && after.start <=val)) return;
28         
29         if (pre!=null && pre.end==val-1){
30             itvlSet.remove(pre);
31             itvl.start = pre.start;
32         }
33         if (after!=null && after.start==val+1){
34             itvlSet.remove(after);
35             itvl.end = after.end;
36         }
37         itvlSet.add(itvl);
38     }
39     
40     public List<Interval> getIntervals() {
41         return new ArrayList<Interval>(itvlSet);
42         
43     }
44     
45     TreeSet<Interval> itvlSet;
46 }
47 
48 /**
49  * Your SummaryRanges object will be instantiated and called as such:
50  * SummaryRanges obj = new SummaryRanges();
51  * obj.addNum(val);
52  * List<Interval> param_2 = obj.getIntervals();
53  */