Rate Limiter - Amazon Top Interview Questions

                        Solution in C++ :

class RateLimiter {
    public:
    RateLimiter(int expire) : limitThreshold(expire) {
    }  // Remember the limit value

    bool limit(int uid, int timestamp) {
        // If the new request came later than minimum allowed we return false and create a new
        // minimum allowed request time
        if (timestamp >= lastTime[uid]) {
            lastTime[uid] = timestamp + limitThreshold;
            return false;
        }
        return true;  // Reject the request
    }

    private:
    unordered_map<int, int> lastTime;  // Storage of uid and minimum allowed request time
                                       // (initialized to 0 when the first requests comes)
    int limitThreshold;                // Limit value
};
                    

                        Solution in Java :

import java.util.*;

class RateLimiter {
    public int expire;
    public HashMap<Integer, Integer> hm = new HashMap<>();
    public RateLimiter(int expire) {
        this.expire = expire;
    }

    public boolean limit(int uid, int timestamp) {
        if (hm.containsKey(uid)) {
            if (hm.get(uid) <= timestamp) {
                hm.put(uid, timestamp + expire);
                return false;
            }
            return true;

        } else {
            hm.put(uid, timestamp + expire);
            return false;
        }
    }
}
                    

                        Solution in Python : 
                            
class RateLimiter:
    def __init__(self, expire):
        self.expire = expire
        self.lastCall = defaultdict(lambda: -1)

    def limit(self, uid, timestamp):
        last = self.lastCall[uid]
        if last == -1 or last + self.expire <= timestamp:
            self.lastCall[uid] = timestamp
            return False
        return True