Interval_List_Intersections.py

"""
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:
    def intervalIntersection(self, A: List[List[int]], B: List[List[int]]) -> List[List[int]]:
        res = []
        i = j = 0
        while i<len(A) and j<len(B):
            low = max(A[i][0],  B[j][0])
            high = min(A[i][1], B[j][1])
            if (low <= high):
                res.append([low, high])
            if A[i][1] < B[j][1]:
                i += 1
            else:
                j += 1
        return res