352. Data Stream as Disjoint Intervals

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?

/**
 * Definition for an interval.
 * public class Interval {
 *     int start;
 *     int end;
 *     Interval() { start = 0; end = 0; }
 *     Interval(int s, int e) { start = s; end = e; }
 * }
 */
class SummaryRanges {

    /** Initialize your data structure here. */
    TreeSet<Interval> set;
    public SummaryRanges() {
        Comparator<Interval> com = new Comparator<Interval>() {
            public int compare(Interval a, Interval b) {
                return a.start - b.start;
            }
        };
        set = new TreeSet(com);
    }
    
    public void addNum(int val) {
        Interval cur = new Interval(val, val);
        Interval pre = set.floor(cur);
        Interval next = set.ceiling(cur);
        if((pre != null && (pre.end >= val)) || (next != null && (next.start <= val))) {
            return;
        }
        if (pre != null && pre.end == val - 1) {
            
            set.remove(pre);
            cur.start = pre.start;
        }
        if (next != null && next.start == val + 1) {
            set.remove(next);
            cur.end = next.end;
        }
           set.add(cur);
    }
    
    public List<Interval> getIntervals() {
        return new ArrayList<Interval>(set);
    }
}