1892. Page Recommendations II π
Description
Table: Friendship
+---------------+---------+ | Column Name | Type | +---------------+---------+ | user1_id | int | | user2_id | int | +---------------+---------+ (user1_id, user2_id) is the primary key (combination of columns with unique values) for this table. Each row of this table indicates that the users user1_id and user2_id are friends.
Table: Likes
+-------------+---------+ | Column Name | Type | +-------------+---------+ | user_id | int | | page_id | int | +-------------+---------+ (user_id, page_id) is the primary key (combination of columns with unique values) for this table. Each row of this table indicates that user_id likes page_id.
You are implementing a page recommendation system for a social media website. Your system will recommend a page to user_id
if the page is liked by at least one friend of user_id
and is not liked by user_id
.
Write a solution to find all the possible page recommendations for every user. Each recommendation should appear as a row in the result table with these columns:
user_id
: The ID of the user that your system is making the recommendation to.page_id
: The ID of the page that will be recommended touser_id
.friends_likes
: The number of the friends ofuser_id
that likepage_id
.
Return the result table in any order.
The result format is in the following example.
Example 1:
Input: Friendship table: +----------+----------+ | user1_id | user2_id | +----------+----------+ | 1 | 2 | | 1 | 3 | | 1 | 4 | | 2 | 3 | | 2 | 4 | | 2 | 5 | | 6 | 1 | +----------+----------+ Likes table: +---------+---------+ | user_id | page_id | +---------+---------+ | 1 | 88 | | 2 | 23 | | 3 | 24 | | 4 | 56 | | 5 | 11 | | 6 | 33 | | 2 | 77 | | 3 | 77 | | 6 | 88 | +---------+---------+ Output: +---------+---------+---------------+ | user_id | page_id | friends_likes | +---------+---------+---------------+ | 1 | 77 | 2 | | 1 | 23 | 1 | | 1 | 24 | 1 | | 1 | 56 | 1 | | 1 | 33 | 1 | | 2 | 24 | 1 | | 2 | 56 | 1 | | 2 | 11 | 1 | | 2 | 88 | 1 | | 3 | 88 | 1 | | 3 | 23 | 1 | | 4 | 88 | 1 | | 4 | 77 | 1 | | 4 | 23 | 1 | | 5 | 77 | 1 | | 5 | 23 | 1 | +---------+---------+---------------+ Explanation: Take user 1 as an example: - User 1 is friends with users 2, 3, 4, and 6. - Recommended pages are 23 (user 2 liked it), 24 (user 3 liked it), 56 (user 3 liked it), 33 (user 6 liked it), and 77 (user 2 and user 3 liked it). - Note that page 88 is not recommended because user 1 already liked it. Another example is user 6: - User 6 is friends with user 1. - User 1 only liked page 88, but user 6 already liked it. Hence, user 6 has no recommendations. You can recommend pages for users 2, 3, 4, and 5 using a similar process.
Solutions
Solution 1
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