Interval List Intersections

Given two lists of closed intervals, each list of intervals is pairwise disjoint and in sorted order.

Return the intersection of these two interval lists.

(Formally, 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 is either empty, or can be represented as a closed interval.  For example, the intersection of [1, 3] and [2, 4] is [2, 3].)

Example 1:

Input: A = [[0,2],[5,10],[13,23],[24,25]], B = [[1,5],[8,12],[15,24],[25,26]]
Output: [[1,2],[5,5],[8,10],[15,23],[24,24],[25,25]]
Reminder: The inputs and the desired output are lists of Interval objects, and not arrays or lists.

 class Solution {
     public int[][] intervalIntersection(int[][] A, int[][] B) {
         if (A == null || A.length ==  || B == null || B.length == ) {
             return new int[][];
         }

         int m = A.length, n = B.length;
         int i = , j = ;
         List<int[]> res = new ArrayList<>();
         while (i < m && j < n) {
             int[] a = A[i];
             int[] b = B[j];

             // find the overlap... if there is any...
             int startMax = Math.max(a[], b[]);
             int endMin = Math.min(a[], b[]);

             if (endMin >= startMax) {
                 res.add(new int[]{startMax, endMin});
             }

             //update the pointer with smaller end value...
             if (a[] == endMin) { i++; }
             if (b[] == endMin) { j++; }
         }
         return res.toArray(new int[][]);
     }
 }