How do you solve Group Sold Products By The Date on LeetCode?

Group Sold Products By The Date (LeetCode #1484) 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: Using a dictionary to group data can significantly reduce time complexity.

What is the brute force solution for Group Sold Products By The Date?

The brute force approach for Group Sold Products By The Date is Brute Force, with O(n²) time complexity and O(1) space complexity. In the brute-force approach, we will iterate through the entire list of sales for each unique date, collecting products sold on that date. This method is straightforward but inefficient due to repeated checks. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Group Sold Products By The Date?

Group Sold Products By The Date uses the following concepts: Database. The recommended patterns to study are: Hash Map, Array.

What are the interview tips for Group Sold Products By The Date?

Always clarify the requirements before diving into coding. Think about edge cases, such as duplicate products or no sales on a date. Practice writing SQL queries as they are common in data-related interviews.

What are common mistakes when solving Group Sold Products By The Date?

Not using DISTINCT when counting products, leading to incorrect counts. Forgetting to sort the product names before concatenating.

#1484

Group Sold Products By The Date

Easy

DatabaseHash MapArray

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 approach, we will use a single pass through the data to build a dictionary that groups products by date. This reduces the number of iterations needed, making it much faster.

⚙️

Algorithm

4 steps

1Step 1: Initialize a dictionary to map each sell_date to a set of products.
2Step 2: Iterate through each row in the Activities table, adding products to the corresponding date in the dictionary.
3Step 3: For each date, convert the set of products to a sorted list and prepare the output format.
4Step 4: Sort the final output by sell_date and return the result.

solution.py4 lines

1SELECT sell_date, COUNT(DISTINCT product) AS num_sold, GROUP_CONCAT(DISTINCT product ORDER BY product) AS products
2FROM Activities
3GROUP BY sell_date
4ORDER BY sell_date;

ℹ

Complexity note: The time complexity is O(n) because we only need to iterate through the list once to build our dictionary, and the space complexity is O(n) due to storing the products in a dictionary.

1Using a dictionary to group data can significantly reduce time complexity.
2Sorting the product names lexicographically is essential for the output format.

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