LEETCODE 986:WHILE INTERVAL PATTERN:Mastering Interval List Intersections with Efficient Solutions

Welcome to our comprehensive tutorial on solving LeetCode Problem 986, "Interval List Intersections." In this video, we will provide you with a detailed explanation of the problem, guide you through the process of developing an efficient solution, and demonstrate how to handle various edge cases. Whether you are preparing for coding interviews or looking to enhance your algorithmic skills, this video will offer valuable insights and practical techniques.
Introduction:
In this tutorial, we will tackle LeetCode Problem 986, which involves finding the intersections between two lists of intervals. Interval problems are common in coding interviews, and understanding how to handle them efficiently is crucial for any aspiring software engineer.
Problem Statement:
Given two lists of closed intervals, each list of intervals is pairwise disjoint and in sorted order. Our task is to return the intersection of these two interval lists. A closed interval [a, b] includes all the real numbers x with a lt or eq x lt or eq b. The intersection of two closed intervals is a set of points that are common to both intervals.
Understanding the Problem:
To better understand the problem, let us break it down:
We have two lists of intervals, and we need to find all the overlapping intervals.
An interval [a, b] overlaps with [c, d] if there is some x such that a lt or eq x lt or eq b and c lt or eq x lt or eq d.
Key Concepts:
To solve this problem efficiently, we need to grasp the following concepts:
Interval Overlap: Understanding how to determine if two intervals overlap.
Two-pointer Technique: Utilizing two pointers to iterate through the lists and find intersections.
Sorting: Ensuring the intervals are in sorted order to simplify the intersection logic.
Step-by-Step Solution:
We will employ the two-pointer technique to traverse both lists of intervals simultaneously. Here are the steps we will follow:
Initialization: Start with two pointers, one for each list of intervals.
Iterate Through Lists: Compare the current intervals from both lists to check for overlap.
Find Intersection: If the intervals overlap, determine the intersection and add it to the result list.
Move Pointers: Move the pointer that points to the interval that finishes first.
Repeat: Continue the process until we have traversed both lists.
Visualization:
To help you visualize the process, we will use diagrams to illustrate how the two-pointer technique works. Visual aids can make it easier to understand the comparisons and movements of the pointers involved in finding intersections.
Example Walkthrough:
We will walk through a detailed example to demonstrate how the algorithm works. Consider the following two lists of intervals:
List A: [ [1, 3], [5, 6], [7, 9] ]
List B: [ [2, 3], [5, 7] ]
By applying our algorithm, we will find the intersections:
[1, 3] and [2, 3] intersect at [2, 3]
[5, 6] and [5, 7] intersect at [5, 6]
[7, 9] and [5, 7] intersect at [7, 7]
Edge Cases:
We will also discuss various edge cases to ensure our solution is robust. Some edge cases include:
No Overlap: If there are no overlapping intervals, the result should be an empty list.
Single List Empty: If one of the lists is empty, the result should also be an empty list.
Nested Intervals: If one interval is completely within another, the intersection should be the smaller interval.
Optimization:
Our approach ensures that we traverse both lists of intervals only once, making it efficient with a time complexity of O(m + n), where m and n are the lengths of the two lists. The space complexity is O(1) for the pointers, but the output list will take up space proportional to the number of intersections found.
Conclusion:
By the end of this video, you will have a solid understanding of how to find the intersections between two lists of intervals using the two-pointer technique. This problem is a great example of how efficient algorithms can simplify complex tasks and is a valuable addition to your problem-solving toolkit.
Call to Action:
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Additional Resources:
For further reading and practice, here are some additional resources:
LeetCode Problem 986: [Link to problem on LeetCode]
Two-pointer Technique Explained: [Link to tutorial]
Interval Problems in Algorithms: [Link to article]
Thank you for watching, and we hope this tutorial helps you ace your coding interviews and improve your problem-solving skills. See you in the next video

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