My code:

/**
 * 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; }
 * }
 */
public class SummaryRanges {
    TreeMap<Integer, Interval> map = new TreeMap<Integer, Interval>();
    /** Initialize your data structure here. */
    public SummaryRanges() {
        
    }
    
    public void addNum(int val) {
        if (map.containsKey(val)) {
            return;
        }
        Integer l = map.lowerKey(val);
        Integer h = map.higherKey(val);
        if (l != null && h != null && map.get(l).end + 1 == val && val + 1 == h) {
            map.put(l, new Interval(l, map.get(h).end));
            map.remove(h);
        }
        else if (l != null && map.get(l).end + 1 >= val) {
            map.put(l, new Interval(l, Math.max(map.get(l).end, val)));
        }
        else if (h != null && val >= h - 1) {
            map.put(val, new Interval(val, map.get(h).end));
            map.remove(h);
        }
        else {
            map.put(val,new Interval(val, val));
        }
    }
    
    public List<Interval> getIntervals() {
        return new ArrayList<Interval>(map.values());
    }
}

/**
 * Your SummaryRanges object will be instantiated and called as such:
 * SummaryRanges obj = new SummaryRanges();
 * obj.addNum(val);
 * List<Interval> param_2 = obj.getIntervals();
 */

reference:
https://discuss.leetcode.com/topic/46887/java-solution-using-treemap-real-o-logn-per-adding

感觉这道题目没什么意思。
主要就是熟悉下 TreeMap
他的特点就是 lowerKey(), higherKey()

Anyway, Good luck, Richardo! — 09/29/2016