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How to Solve User Activity for the Past 30 Days I Problem
Master the User Activity for the Past 30 Days I LeetCode problem with undetectable real-time assistance. Get instant solutions and explanations during your coding interviews.
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Start Free for WindowsEasy#1141
LeetCode ProblemUser Activity for the Past 30 Days I
Table: Activity Write a solution to find the daily active user count for a period of 30 days ending 2019-07-27 inclusively. A user was active on someday if they made at least one activity on that day. Return the result table in any order. The result format is in the following example.
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Problem Breakdown
Understanding the User Activity for the Past 30 Days I Problem
Let's break down this LeetCode problem and understand what makes it challenging in interview settings.
Problem Statement
Table: Activity Write a solution to find the daily active user count for a period of 30 days ending 2019-07-27 inclusively. A user was active on someday if they made at least one activity on that day. Return the result table in any order. The result format is in the following example.
EasyProblem #1141
LeetCodeUser Activity for the Past 30 Days I
Related Topics
Database
How Phantom Code Helps
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Examples
# Example 1
Input
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Output
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# Example 2
Input
Activity table: +---------+------------+---------------+---------------+ | user_id | session_id | activity_date | activity_type | +---------+------------+---------------+---------------+ | 1 | 1 | 2019-07-20 | open_session | | 1 | 1 | 2019-07-20 | scroll_down | | 1 | 1 | 2019-07-20 | end_session | | 2 | 4 | 2019-07-20 | open_session | | 2 | 4 | 2019-07-21 | send_message | | 2 | 4 | 2019-07-21 | end_session | | 3 | 2 | 2019-07-21 | open_session | | 3 | 2 | 2019-07-21 | send_message | | 3 | 2 | 2019-07-21 | end_session | | 4 | 3 | 2019-06-25 | open_session | | 4 | 3 | 2019-06-25 | end_session | +---------+------------+---------------+---------------+
Output
+------------+--------------+ | day | active_users | +------------+--------------+ | 2019-07-20 | 2 | | 2019-07-21 | 2 | +------------+--------------+
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Solve User Activity for the Past 30 Days I — Table: Activity Write a solution to find the daily active user count for a perio...
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def solve(input):
# Optimal O(n) solution
return result
Time: O(n) | Space: O(n)
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Frequently Asked Questions
Common questions about solving User Activity for the Past 30 Days I and using Phantom Code during coding interviews.
How does Phantom Code help me solve coding problems like User Activity for the Past 30 Days I during interviews?
Phantom Code generates complete solutions instantly with proper complexity analysis, letting you focus on explaining your approach and demonstrating problem-solving skills rather than getting stuck on implementation details during high-pressure situations.
What if the interviewer asks follow-up questions or modifications to problems like User Activity for the Past 30 Days I?
Phantom Code adapts in real-time. Screenshot the modified problem or use audio mode to capture the interviewer's follow-up, and get an updated solution within seconds — including edge cases and optimizations.
Can Phantom Code help me communicate my solution for problems like User Activity for the Past 30 Days I?
Yes. Phantom Code provides step-by-step approach explanations with 3 progressive thoughts, so you can walk through your solution naturally. It also provides time and space complexity analysis to discuss trade-offs.
How does Phantom Code assist with different programming languages for User Activity for the Past 30 Days I type problems?
Phantom Code supports 11 programming languages including Python, Java, C++, JavaScript, TypeScript, Go, Rust, Ruby, Swift, Kotlin, and C#. Set your preferred language and get idiomatic solutions.
What coding mistakes does Phantom Code help me avoid during User Activity for the Past 30 Days I interviews?
Phantom Code catches common mistakes like off-by-one errors, missing edge cases, incorrect base conditions, and suboptimal approaches. It provides clean, well-structured code that handles all edge cases.
Is Phantom Code detectable when solving problems like User Activity for the Past 30 Days I during live interviews?
No. Phantom Code runs as an invisible desktop overlay that doesn't appear in screen shares, recordings, or proctoring software. It works with Zoom, HackerRank, CodeSignal, CoderPad, and all major platforms.
How does Phantom Code help when I'm struggling with User Activity for the Past 30 Days I style questions under pressure?
The AI provides structured guidance: first the approach (what algorithm/data structure to use and why), then the implementation with clean code, and finally complexity analysis. This helps you think clearly even under pressure.
Does Phantom Code work for the coding platforms used in User Activity for the Past 30 Days I interviews?
Yes. Phantom Code works with all major coding platforms including LeetCode, HackerRank, CodeSignal, CoderPad, HackerEarth, and any browser-based coding environment.
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