How do you solve Article Views I on LeetCode?

Article Views I (LeetCode #1148) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n) time complexity and O(n) space complexity. Key insight: Authors can only view their own articles if their author_id matches their viewer_id.

What algorithm or data structure is used to solve Article Views I?

Article Views I uses the following concepts: Database. The recommended patterns to study are: Hash Map, Array.

What are the interview tips for Article Views I?

Always clarify the requirements before jumping into coding. Think about edge cases, such as no authors viewing their own articles. Practice writing SQL queries to become familiar with syntax and logic.

What are common mistakes when solving Article Views I?

Not using DISTINCT, leading to duplicate author_ids in the result. Forgetting to sort the result set before returning.

Article Views I — LeetCode #1148 (Easy)

Tags: Database

Related patterns: Hash Map, Array

Brute Force approach

Time complexity: O(n²). Space complexity: O(1).

In the brute-force approach, we will check each article's views and see if the author is also a viewer. This is straightforward but inefficient, as it requires checking every view for every article.

The time complexity is O(n²) because for each row, we are checking against all other rows to see if the author viewed their own article, leading to a nested iteration.

Step 1: Iterate through each row in the Views table.
Step 2: For each row, check if the author_id is the same as the viewer_id.
Step 3: If they match, add the author_id to a result set to avoid duplicates.
Step 4: After processing all rows, sort the result set in ascending order.
Step 5: Return the sorted result set.

1. Row 1: author_id = 3, viewer_id = 5 (no match) 2. Row 2: author_id = 3, viewer_id = 6 (no match) 3. Row 3: author_id = 7, viewer_id = 7 (match, add 7) 4. Row 4: author_id = 7, viewer_id = 6 (no match) 5. Row 5: author_id = 7, viewer_id = 1 (no match) 6. Row 6: author_id = 4, viewer_id = 4 (match, add 4) Final result: [4, 7]

Optimal Solution approach

Time complexity: O(n). Space complexity: O(n).

In the optimal solution, we can directly filter the rows where the author is also the viewer in a single pass, making it much more efficient.

The time complexity is O(n) because we only need to scan through the rows once to find matches, and the space complexity is O(n) due to storing unique author_ids.

Step 1: Use a SELECT statement to filter rows where author_id equals viewer_id.
Step 2: Use DISTINCT to ensure that we only get unique author_ids.
Step 3: Sort the results by author_id in ascending order.

Key Insights

Authors can only view their own articles if their author_id matches their viewer_id.
Using DISTINCT helps in eliminating duplicate entries in the result.

Common Mistakes

Not using DISTINCT, leading to duplicate author_ids in the result.
Forgetting to sort the result set before returning.

Interview Tips

Always clarify the requirements before jumping into coding.
Think about edge cases, such as no authors viewing their own articles.
Practice writing SQL queries to become familiar with syntax and logic.

#1148

Article Views I

Easy

Database↗Hash Map↗Array↗

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n²)	O(n)
Space	O(1)	O(n)

💡

Intuition

Time O(n)Space O(n)

In the optimal solution, we can directly filter the rows where the author is also the viewer in a single pass, making it much more efficient.

⚙️

Algorithm

3 steps

1Step 1: Use a SELECT statement to filter rows where author_id equals viewer_id.
2Step 2: Use DISTINCT to ensure that we only get unique author_ids.
3Step 3: Sort the results by author_id in ascending order.

solution.py4 lines

1SELECT DISTINCT author_id AS id
2FROM Views
3WHERE author_id = viewer_id
4ORDER BY id;

ℹ

Complexity note: The time complexity is O(n) because we only need to scan through the rows once to find matches, and the space complexity is O(n) due to storing unique author_ids.

1Authors can only view their own articles if their author_id matches their viewer_id.
2Using DISTINCT helps in eliminating duplicate entries in the result.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.