Social Network Likes Count

A social media platform keeps records of mutual likes between pairs of users. Each record contains two user identifiers and two integer values: the number of likes from the first user to the second, and the number of likes from the second to the first. For instance, the record (Alice, Bob, 7, 3) means that Alice liked Bob 7 times and Bob liked Alice 3 times.

Your task is to design an appropriate data structure to hold a set of these records, and then implement a lookup function getLikes(userA, userB) that returns the number of likes userA directed toward userB. You may assume that every queried pair (userA, userB) will be present among the stored records.

For the examples below, assume the stored records are:

• (Alice, Bob, 10, 5)
• (Charlie, Dave, 3, 7)
• (Eve, Frank, 0, 2)
• (Grace, Helen, 4, 0)

Example 1:

Input: Alice Bob
Output: 10

Explanation: Alice liked Bob 10 times.

Example 2:

Input: Frank Eve
Output: 2

Example 3:

Input: Helen Grace
Output: 0

Constraints:

• Number of stored records ≤ 10,000.
• User names consist of uppercase and lowercase letters and are at most 20 characters long.
• Each queried pair is guaranteed to have a matching record.