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 <= 1000firstList.length + secondList.length >= 10 <= starti < endi <= 109endi < starti+10 <= startj < endj <= 109 endj < startj+1In this approach, we use a two-pointer technique to traverse both lists of intervals simultaneously. We check for intersections between the intervals pointed by our two pointers. If there's an intersection, we record it. We then progress the pointer that points to the interval with the smaller endpoint. This ensures that we consider new overlapping possibilities as the intervals in each list are disjoint and sorted.
We use pointers a and b to iterate over firstList and secondList respectively. We find the maximum start and minimum end for the current intervals pointed by these pointers to determine overlap. If there's an overlap, it is added to the result list. We move the pointer with the smaller endpoint to ensure progress.
C++
Java
Python
C#
JavaScript
Time Complexity: O(n + m), where n and m are the number of intervals in the two lists. This is because we process each interval at most once.
Space Complexity: O(1), apart from the output space, since only a few variables are used.
Merge Intervals - Sorting - Leetcode 56 • NeetCode • 190,650 views views
Watch 9 more video solutions →Practice Interval List Intersections with our built-in code editor and test cases.
Practice on FleetCode