355. Design Twitter

📝 Problem Details

• Title: 355. Design Twitter
• Link: https://leetcode.com/problems/design-twitter/
• Difficulty: Medium
• Tags/Categories: {{tags/categories}}

*This question was asked during an OOP/OOD mock interview, so the thought and implementation process varied from a traditional LeetCode question

💻 Implementation of Solution

class Twitter {
private:
    long long time;
    unordered_map<int, set<int>> following;
    unordered_map<int,vector<pair<int,int>>>tweets;
 
public:
    Twitter() {
        time = 0;
    }
    
    void postTweet(int userId, int tweetId) {
        tweets[userId].push_back({time++, tweetId});
    }
    
    vector<int> getNewsFeed(int userId) {
        vector<int>res;
        priority_queue<pair<int,int>>pq;
        for(auto it:tweets[userId])pq.push(it);
        for(int follower:following[userId]){
            for(auto it:tweets[follower])pq.push(it);
        }
        while(!pq.empty() && res.size()<10){
            res.push_back(pq.top().second);
            pq.pop();
        }
        return res;
    }
    
    void follow(int followerId, int followeeId) {
        following[followerId].insert(followeeId);
    }
    
    void unfollow(int followerId, int followeeId) {
        following[followerId].erase(followeeId);   
    }
};
 
/**
 * Your Twitter object will be instantiated and called as such:
 * Twitter* obj = new Twitter();
 * obj->postTweet(userId,tweetId);
 * vector<int> param_2 = obj->getNewsFeed(userId);
 * obj->follow(followerId,followeeId);
 * obj->unfollow(followerId,followeeId);
 */