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]]
Note:
0 <= A.length < 1000
0 <= B.length < 1000
0 <= A[i].start, A[i].end, B[i].start, B[i].end < 10^9
class Solution:
    def intervalIntersection(self, A: List[List[int]], B: List[List[int]]) -> List[List[int]]:
        if not A or not B:
            return []
        res = []
        i = j = 0
        while i < len(A) and j < len(B):
            s, e = max(A[i][0], B[j][0]), min(A[i][1], B[j][1])
            if s <= e:
                res.append([s, e])   
            if A[i][1] < B[j][1]:
                i += 1
            else:
                j += 1

        return res

class Solution:
    def intervalIntersection(self, A: List[List[int]], B: List[List[int]]) -> List[List[int]]:
        if not A or not B:
            return []
        res = []
        i = j = 0
        while i < len(A) and j < len(B):
            s, e = max(A[i][0], B[j][0]), min(A[i][1], B[j][1])
            if s <= e:
                res.append([s, e])   
            if A[i][1] < B[j][1]:
                i += 1
            else:
                j += 1

        return res
