Design follow/follower classes

Object-Oriented Design: Follow / Followers Relationship

Design a small set of classes for a social product where users can follow and unfollow each other.

Requirements

• Each user can follow many other users.
• Each user can be followed by many other users.
• Support querying:
  • getFollowers(user) → all users who follow user
  • getFollowing(user) → all users whom user follows
  • isFollowing(a, b) → whether user a follows user b
  • isMutual(a, b) → whether a follows b and b follows a
• Handle edge cases:
  • following yourself (decide behavior)
  • repeated follow/unfollow calls should be idempotent

Constraints (assume)

• You may assume all users are already created and identified by a unique userId .
• You may choose in-memory data structures; optionally discuss how this maps to persistence.