LeetCode 1141: User Activity for the Past 30 Days I Solution
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1141. User Activity for the Past 30 Days I
Problem Explanation
Explanation:
To solve this problem, we need to count the number of active users for each day within a 30-day period ending on a specific date. We can achieve this by grouping the activities by user and date, and then counting the distinct users for each date.
- Filter the activities within the 30-day period ending on the target date.
- Group the activities by activity_date and user_id.
- Count the distinct user_ids for each activity_date.
- Output the result for days with at least one active user.
Time Complexity: O(n), where n is the number of rows in the Activity table. Space Complexity: O(n) for storing the intermediate results.
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Solution Code
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