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.

Solution：TreeMap

思路：
Time Complexity: O(NlogN) Space Complexity: O(N)

Solution Code：

public class Solution {
    public int[] findRightInterval(Interval[] intervals) {
        int[] res = new int[intervals.length];
        TreeMap<Integer, Integer> map = new TreeMap<>();
        
        for(int i=0;i<intervals.length;i++) map.put(intervals[i].start, i);
        for(int i=0;i<intervals.length;i++) {
            Integer key = map.ceilingKey(intervals[i].end); // direct right
            res[i] = key !=null ? map.get(key) : -1;
        }
        return res;
    }
}