What is the time complexity of Determine if Two Events Have Conflict?

The optimal solution has a time complexity of O(1).

What data structures are used to solve Determine if Two Events Have Conflict?

This problem uses Array, String. Understanding these concepts is essential for solving this Easy problem efficiently.

What are the key insights for solving Determine if Two Events Have Conflict?

Insight 1: The events overlap if and only if the end time of one event is not before the start time of the other event. Insight 2: String comparison can be directly used to compare times in HH:MM format since lexicographical ordering aligns with time ordering.

Which companies ask LeetCode 2446. Determine if Two Events Have Conflict in interviews?

This problem is frequently asked at Goldman Sachs.

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Determine if Two Events Have Conflict - LeetCode 2446 Solution

Determine if Two Events Have Conflict - Complete Solution Guide

Determine if Two Events Have Conflict is LeetCode problem 2446, a Easy level challenge. This complete guide provides step-by-step explanations, multiple solution approaches, and optimized code in python3, java, cpp, c.

Problem Statement

You are given two arrays of strings that represent two inclusive events that happened on the same day , event1 and event2 , where: event1 = [startTime 1 , endTime 1 ] and event2 = [startTime 2 , endTime 2 ] . Event times are valid 24 hours format in the form of HH:MM . A conflict happens when two events have some non-empty intersection (i.e., some moment is common to both events). Return true if there is a conflict between two events. Otherwise, return false . Example 1: Input: event1 = ["01:15"

Detailed Explanation

The problem asks you to determine if two events, each represented by a start and end time in HH:MM format, overlap. The input consists of two arrays, `event1` and `event2`, each containing two strings representing the start and end times of an event. The output is a boolean value: `true` if the events overlap (have any time in common), and `false` otherwise. For example, if event1 is ["01:15", "02:00"] and event2 is ["02:00", "03:00"], they overlap at 02:00, so the output is `true`. If event1 is ["10:00", "11:00"] and event2 is ["14:00", "15:00"], they don't overlap, and the output is `false`.

Solution Approach

The provided code utilizes a concise approach to determine event overlap. It directly compares the start and end times of the two events using string comparison. The logic hinges on the observation that if there is no overlap, either the end time of event1 is strictly before the start time of event2 OR the end time of event2 is strictly before the start time of event1. The solution negates this condition, effectively returning `true` only if an overlap exists.

Step-by-Step Algorithm

Step 1: Compare the end time of `event1` (event1[1]) with the start time of `event2` (event2[0]).
Step 2: Compare the end time of `event2` (event2[1]) with the start time of `event1` (event1[0]).
Step 3: If either comparison in Step 1 or Step 2 shows that one event's end time is strictly before the other event's start time, there's no overlap, so return `false`. Otherwise, there is an overlap, return `true`.

Key Insights

Insight 1: The events overlap if and only if the end time of one event is not before the start time of the other event.
Insight 2: String comparison can be directly used to compare times in HH:MM format since lexicographical ordering aligns with time ordering.
Insight 3: The solution efficiently avoids explicit time conversion to numerical representations, leveraging the built-in string comparison functionalities.

Complexity Analysis

Time Complexity: O(1)

Space Complexity: O(1)

Topics

This problem involves: Array, String.

Companies

Asked at: Goldman Sachs.

Determine if Two Events Have Conflict | LeetCode 2446

Easy

Array String

Time: O(1)Space: O(1)

Solution Code

Available in:

class Solution {
    public boolean haveConflict(String[] event1, String[] event2) {
        return !(event1[1].compareTo(event2[0]) < 0 || event2[1].compareTo(event1[0]) < 0);
    }
}

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Problem Info

Description

Problem 2446: Determine if Two Events Have Conflict - Detailed explanation and solution approaches.

Topics

Array String

Companies

Goldman Sachs

Stats

Difficulty:Easy

Languages:4

Companies:1

Problem #:2446

Problem Explanation

💡

Think Before You Code

🤔 Ask Yourself

→What is the input? What output do I need?
→Can I solve a smaller version of this problem first?
→What patterns have I seen in similar problems?

✏️ Try This First

Before looking at the solution, try to solve it on paper with a simple example!

🚀 Try on LeetCode

Solution Approach

📋

Step-by-Step Solution

3 steps

1
Step 1: Compare the end time of `event1` (event1[1]) with the start time of `event2` (event2[0]).
2
Step 2: Compare the end time of `event2` (event2[1]) with the start time of `event1` (event1[0]).
3
Step 3: If either comparison in Step 1 or Step 2 shows that one event's end time is strictly before the other event's start time, there's no overlap, so return `false`. Otherwise, there is an overlap, return `true`.

💡

Pro Tip for Students

Try tracing through each step with a small example on paper before coding. Understanding "why" each step happens is more important than memorizing the code!

⚡

Complexity Analysis

⏱️

Time Complexity

O(1)

⚡ Constant time - Super fast! Same speed regardless of input size.

💾

Space Complexity

O(1)

💪 Constant space - Uses same memory regardless of input!

📝

Why?

The solution performs a fixed number of string comparisons regardless of the input size. String comparison in most implementations has a time complexity of O(1) for strings of fixed length (as constrained by the problem statement). No additional data structures are used beyond the input arrays; therefore, space complexity is constant.

📖New to Big O? Click to learn more

Big O Notation - Quick Guide

O(1)Best - Instant

O(log n)Excellent - Binary Search

O(n)Good - One loop

O(n log n)OK - Sorting

O(n²)Slow - Nested loops

O(2ⁿ)Very Slow - Recursion

Alternative Approaches

Time Conversion to Minutes

Convert HH:MM times to total minutes since midnight. Then, check for overlap using numerical comparison.

Time: O(1)Space: O(1)

Trade-offs: This approach might be slightly less concise but could offer better readability for some programmers. However, it introduces the overhead of time conversion, which would negligibly affect overall performance in this specific scenario.

✨

Key Insights

1Insight 1: The events overlap if and only if the end time of one event is not before the start time of the other event.
2Insight 2: String comparison can be directly used to compare times in HH:MM format since lexicographical ordering aligns with time ordering.
3Insight 3: The solution efficiently avoids explicit time conversion to numerical representations, leveraging the built-in string comparison functionalities.

📚

Key Terms Explained

For Students

Array

A collection of items stored at contiguous memory locations. Like a row of boxes.

String

A sequence of characters. Like a word or sentence in programming!

Edge Cases

Edge case 1: Events that start and end at the exact same time. The solution correctly handles this case, as there is an overlap (intersection).
Edge case 2: Events with start and end times that are reversed (invalid input). The provided solution does not explicitly handle this, but the implicit assumption is that the input always follows the constraint `startTime <= endTime`.

⚠️

Common Mistakes to Avoid

✗Common mistake 1: Incorrectly handling the logic of the overlap condition. For example, using an 'and' instead of an 'or' in the comparison could lead to false negatives.

✗Common mistake 2: Forgetting to account for cases where the events share only a single point in time (e.g., event1 ends exactly when event2 starts).

✅

Learning Tip

Every mistake is a learning opportunity! When you make an error, understand why it happened before moving on.

🌍

Where is This Used in Real Life?

💼Real-world scenario 1: Scheduling applications, to check for conflicts between appointments or meetings.

🏦Real-world scenario 2: Resource allocation systems, ensuring that a resource is not double-booked.

💡Understanding real-world applications helps you see the "why" behind algorithms. It's not just about passing interviews—these concepts power the apps and websites you use every day!

Author's Notes

💡 Key Insight

When dealing with arrays, always consider if sorting would simplify the problem. Many array problems have O(n) solutions using hash maps or two-pointer technique.

🎯 Interview Tip

Use this problem to demonstrate clean code practices. Variable naming and code organization matter.

⚠️ Watch Out

Off-by-one errors are the most common mistake. Double-check your loop bounds and array indices.

Written by Saswata Mondal

Software Engineer • Algorithms Enthusiast • Interview Coach

👨‍💻

About the Author

👨‍💻

Saswata MondalAuthor400+ LC Problems

B.Tech CSE, IEM Kolkata | LeetCode Rating: 1672 (Top 15%)

Certified: IBM Java Developer, NPTEL Programming in Java

Last updated: September 15, 2024LeetCode Profile GitHub

This solution has been crafted based on my experience solving 400+ LeetCode problems. Each explanation is designed to help you understand the underlying concepts, not just memorize the code.

Community Tips & Insights

The key insight here is recognizing the pattern. Once you see it, the solution becomes straightforward.

@AlgoMasterJul 13

I was asked this exact problem at my Google interview. The interviewer wanted me to optimize space complexity.

@InterviewProJul 6

❓

Frequently Asked Questions

What is the most efficient way to solve array problems?

Most array problems can be solved efficiently using techniques like two-pointer approach, sliding window, or hash maps. The key is identifying whether the array is sorted (enabling binary search) or if tracking seen elements (using hash maps) can help achieve O(n) time complexity.

How do I handle string manipulation efficiently?

In languages with immutable strings (Java, Python, C#), use StringBuilder/list to avoid O(n) concatenation cost. Consider using character arrays for in-place modifications. For pattern matching, consider KMP or Rabin-Karp for O(n+m) complexity.

How should I approach easy-level algorithm problems?

Easy problems build foundational skills. Focus on: 1) Understanding the problem completely before coding, 2) Writing clean, readable code, 3) Handling all edge cases (empty input, single element, etc.), 4) Analyzing time and space complexity. Don't skip complexity analysis even for simple solutions.

How should I practice algorithm problems effectively?

Focus on understanding patterns rather than memorizing solutions. After solving a problem, review optimal solutions and understand the intuition. Group similar problems to recognize patterns. Practice explaining your approach out loud. Review problems after a few days to test retention.

What is the optimal approach for "Determine if Two Events Have Conflict"?

For this easy-level Array problem, the key is to identify the core pattern. Analyze the input constraints to determine acceptable time complexity. Consider whether string techniques can optimize the solution. Always handle edge cases and validate your approach with examples before coding.

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