Given a set of intervals, for each of the interval i, check if there exists an interval j whose start point is bigger than or equal to the end point of the interval i, which can be called that j is on the "right" of i.
For any interval i, you need to store the minimum interval j's index, which means that the interval j has the minimum start point to build the "right" relationship for interval i. If the interval j doesn't exist, store -1 for the interval i. Finally, you need output the stored value of each interval as an array.
Note:
- You may assume the interval's end point is always bigger than its start point.
- You may assume none of these intervals have the same start point.
Example 1:
Input: [ [1,2] ]Output: [-1]Explanation: There is only one interval in the collection, so it outputs -1.
Example 2:
Input: [ [3,4], [2,3], [1,2] ]Output: [-1, 0, 1]Explanation: There is no satisfied "right" interval for [3,4].For [2,3], the interval [3,4] has minimum-"right" start point;For [1,2], the interval [2,3] has minimum-"right" start point.
Example 3:
Input: [ [1,4], [2,3], [3,4] ]Output: [-1, 2, -1]Explanation: There is no satisfied "right" interval for [1,4] and [3,4].For [2,3], the interval [3,4] has minimum-"right" start point. 题目含义：
题目给了一堆[起始位置，结束位置]的数组，定义了一个个区间。
任务则是要求对于给定的第I个区间，找到一个最小的j，这里的j的起始位置大于等于I的结束位置。找不到为-1
1 public int[] findRightInterval(Interval[] intervals) { 2 int[] result = new int[intervals.length]; 3 TreeMap map = new TreeMap<>(); 4 for (int i = 0; i < intervals.length; i++) map.put(intervals[i].start, i); 5 for (int i = 0; i < intervals.length; i++) { 6 // lowerEntry、floorEntry、ceilingEntry 和 higherEntry 方法，它们分别返回与小于、小于等于、大于等于、大于给定键的键关联的 Map.Entry 对象。 7 Map.Entry item = map.ceilingEntry(intervals[i].end);//找出大于等于intervals[i].end的key 8 result[i] = (item == null) ? -1 : item.getValue(); 9 }10 return result; 11 }