352. Data Stream as Disjoint Intervals

Q:

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?

A:-----也可以用TreeMap 

思路很直接：  就是用Set记录每个插入的。如果有重复的，就直接忽略
用List记录结果。
用Map记录   每个上下界 对应的interval，没加入一个新的数字，则 检查和修改map和list

/**
 * 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 {
    List<Interval> list ;
    Map<Integer, Interval> map;   // record start and end only 
    Set<Integer> set; // all found numbers
    /** Initialize your data structure here. */
    public SummaryRanges() {
        list = new LinkedList<>();
        map = new HashMap<>();
        set = new HashSet<>();
    }
    
    public void addNum(int val) {
        if(set.contains(val))
            return;
        set.add(val);
        // check val+1
        if(map.containsKey(val+1)){
            Interval after = map.get(val+1);
            after.start = val;
            map.put(val, after);
            if(after.end != val+1)
                map.remove(val+1);
            if(map.containsKey(val-1)){
                Interval before = map.get(val-1);
                list.remove(before);
                after.start = before.start;
                map.put(after.start, after);
                if(before.start != val -1 )
                    map.remove(val-1);
            }
            return;
        }
        // check val -1 
        if(map.containsKey(val-1)){  // cannot contains upper
            Interval before = map.get(val-1);
            before.end = val;
            if(before.start != val -1)
                map.remove(val-1);
            map.put(val,before);
            return;
        }
        // add a new interval, linearly
        Interval tmp = new Interval(val, val);
        for(int i = 0;i< list.size();i++){
            if(list.get(i).start > val){
                map.put(val,tmp);
                list.add(i,tmp);
                return;
            }
        }
        map.put(val, tmp);
        list.add(tmp);
    }
    
    public List<Interval> getIntervals() {
        return list;
    }
}

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

Errors：

记得remove from Map 的时候，需要小心start == end的情况