Logger Rate Limiter

Problem

Design a logger system that receives a stream of messages along with their timestamps. Each unique message should only be printed at most every 10 seconds (i.e. a message printed at timestamp t will prevent other identical messages from being printed until timestamp t + 10).

All messages will come in chronological order. Several messages may arrive at the same timestamp.

Implement the Logger class:

• Logger() Initializes the logger object.
• bool shouldPrintMessage(int timestamp, string message) Returns true if the message should be printed in the given timestamp, otherwise returns false.

Constraints

• 0 <= timestamp <= 109
• Every timestamp will be passed in non-decreasing order (chronological order).
• 1 <= message.length <= 30
• At most 104 calls will be made to shouldPrintMessage.

Solution

The problem Logger Rate Limiter can be solved using a hash map to store the latest timestamp of messages that were successfully printed.

Implementation

class Logger
{
  private:
    unordered_map<string, int> cache;

  public:
    Logger() {}

    bool shouldPrintMessage(int timestamp, string message)
    {
        if (cache[message] <= timestamp)
        {
            cache[message] = timestamp + 10;
            return true;
        }

        return false;
    }
};

/**
 * Your Logger object will be instantiated and called as such:
 * Logger* obj = new Logger();
 * bool param_1 = obj->shouldPrintMessage(timestamp,message);
 */