leetcode - 57.Insert Interval

Insert Interval

Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary).

You may assume that the intervals were initially sorted according to their start times.

Example 1:

Given intervals [1,3],[6,9], insert and merge [2,5] in as [1,5],[6,9].

Example 2:

Given [1,2],[3,5],[6,7],[8,10],[12,16], insert and merge [4,9] in as [1,2],[3,10],[12,16].

This is because the new interval [4,9] overlaps with [3,5],[6,7],[8,10].

Solution:

  public List insert(List intervals, Interval newInterval) {
    intervals.add(newInterval);
    intervals.sort((i1, i2) -> Integer.compare(i1.start, i2.start));

    List<Interval> result = new ArrayList<>();
    int start = intervals.get(0).start;
    int end = intervals.get(0).end;

    for (Interval i : intervals) {
      if (i.start <= end) {
        end = Math.max(i.end, end);
      } else {
        result.add(new Interval(start, end));
        start = i.start;
        end = i.end;
      }
    }
    result.add(new Interval(start, end));
    return result;
  }

Solution2:

better

  public List insert(List intervals, Interval newInterval) {
    int i = 0;
    int len = intervals.size();
    while (i < len && intervals.get(i).end < newInterval.start) {
      i++;
    }
    while (i < intervals.size() && intervals.get(i).start <= newInterval.end) {
      newInterval.start = Math.min(newInterval.start, intervals.get(i).start);
      newInterval.end = Math.max(newInterval.end, intervals.get(i).end);
      intervals.remove(i);
    }
    intervals.add(i, newInterval);
    return intervals;
}