Is Points That Intersect With Cars easy or hard?

LeetCode classifies this problem as Easy. The straightforward set simulation is simple to implement, while the sweep line solution introduces a useful prefix sum technique often used in interval and range update problems.

Points That Intersect With Cars Python/Java solution

Most implementations follow either set simulation or sweep line logic. In Python and Java, iterate through intervals inserting points into a set, or build a difference array and compute prefix sums to count covered positions efficiently.

How to solve Points That Intersect With Cars in O(n)?

Use a sweep line with a difference array. For each interval [l, r], increment diff[l] and decrement diff[r+1]. Compute the prefix sum across the array and count positions where the running value is greater than zero. This processes intervals in O(n) and scans the range once.

What is the best approach for Points That Intersect With Cars?

The sweep line algorithm using a difference array and prefix sum is the best approach. It marks where intervals start and end, then reconstructs coverage with a single prefix sum pass. This runs in O(n + range) time and avoids iterating every point in every interval.

Is Points That Intersect With Cars asked at Google/Amazon/Meta?

Interval coverage and sweep line problems frequently appear in interviews at companies like Google, Amazon, and Meta. While this exact problem may vary, the underlying concepts—interval processing, prefix sums, and range counting—are common interview patterns.

What data structure is used in Points That Intersect With Cars?

Two main data structures are used. The brute force approach uses a Hash Set to store unique covered points. The optimized approach uses an array-based difference array combined with prefix sums to efficiently track interval coverage.

What is the time complexity of Points That Intersect With Cars?

The brute force set simulation runs in O(n * range) time because every point inside each interval may be visited. The sweep line prefix sum approach improves this to O(n + range) by processing only interval boundaries and scanning the coordinate range once.

Description Hints 1 Solution Video 9:24

2848. Points That Intersect With Cars

Easy73.4% acceptance1 company

You are given a 0-indexed 2D integer array nums representing the coordinates of the cars parking on a number line. For any index i, nums[i] = [start_i, end_i] where start_i is the starting point of the i^th car and end_i is the ending point of the i^th car.

Return the number of integer points on the line that are covered with any part of a car.

Example 1:

Input: nums = [[3,6],[1,5],[4,7]]
Output: 7
Explanation: All the points from 1 to 7 intersect at least one car, therefore the answer would be 7.

Example 2:

Input: nums = [[1,3],[5,8]]
Output: 7
Explanation: Points intersecting at least one car are 1, 2, 3, 5, 6, 7, 8. There are a total of 7 points, therefore the answer would be 7.

Constraints:

1 <= nums.length <= 100
nums[i].length == 2
1 <= start_i <= end_i <= 100

Asked at 1 company

Uber

Topics

Hints open one at a time

Hint 1

Sort the array according to first element and then starting from the 0^th index remove the overlapping parts and return the count of non-overlapping points.

9:24

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