public class Solution
extends Object
986 - Interval List Intersections\.
Medium
You are given two lists of closed intervals, `firstList` and `secondList`, where firstList[i] = [starti, endi] and secondList[j] = [startj, endj]. Each list of intervals is pairwise **disjoint** and in **sorted order**.
Return _the intersection of these two interval lists_.
A **closed interval** `[a, b]` (with `a <= b`) denotes the set of real numbers `x` with `a <= x <= b`.
The **intersection** of two closed intervals is a set of real numbers that are either empty or represented as a closed interval. For example, the intersection of `[1, 3]` and `[2, 4]` is `[2, 3]`.
**Example 1:**
**Input:** firstList = \[\[0,2],[5,10],[13,23],[24,25]], secondList = \[\[1,5],[8,12],[15,24],[25,26]]
**Output:** [[1,2],[5,5],[8,10],[15,23],[24,24],[25,25]]
**Example 2:**
**Input:** firstList = \[\[1,3],[5,9]], secondList = []
**Output:** []
**Constraints:**
* `0 <= firstList.length, secondList.length <= 1000`
* `firstList.length + secondList.length >= 1`
* 0 <= starti < endi <= 109
* endi < starti+1
* 0 <= startj < endj <= 109
* endj < startj+1