986. Interval List Intersections
https://leetcode.com/problems/interval-list-intersections/
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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.
Note:
0 <= A.length < 1000
0 <= B.length < 1000
0 <= A[i].start, A[i].end, B[i].start, B[i].end < 10^9
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Clarifying questions
Are input lists sorted
What is expected output when start, end times overlap
What is expected output when any of the input list is empty
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Intuition
Find overlaps with simple formula
lo = Math.max(A.start, B.start)
hi = Math.min(A.end, B.end)
if (lo <= hi) => valid overlap -- add to ans
Increment the pointer of array with min end time, it no longer contributes to ans
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Time - O(A + B)
Space - O(1) - not counting space for ans
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