352. Data Stream as Disjoint Intervals

题目：
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?

解答：
这题用Maptree会通过map.lowerKey, map.higherKey很快定位到当前数所处在哪两个interval之间，从而进行高效的比较与合并。

/

• 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 map;
  / Initialize your data structure here. /
  public SummaryRanges() {
  map = new TreeMap();
  }

  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 == map.get(h).start) {
  map.get(l).end = map.get(h).end;
  map.remove(h);
  } else if (l != null && val getIntervals() {
  return new ArrayList(map.values());
  }
  }

/

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

关键字：leetcode, java, map, val

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