[LeetCode] Logger Rate Limiter

Posted on 2020-04-15 In LeetCode Disqus:

Question:

Design a logger system that receives the stream of messages along with its timestamps; each message should be printed if and only if it is not printed in the last 10 seconds.

Given a message and a timestamp (in seconds granularity), return true if the message should be printed in the given timestamp; otherwise, it returns false.

It is possible that several messages arrive roughly at the same time.

Example:

Logger logger = new Logger();

// logging string "foo" at timestamp 1
logger.shouldPrintMessage(1, "foo"); returns true; 

// logging string "bar" at timestamp 2
logger.shouldPrintMessage(2,"bar"); returns true;

// logging string "foo" at timestamp 3
logger.shouldPrintMessage(3,"foo"); returns false;

// logging string "bar" at timestamp 8
logger.shouldPrintMessage(8,"bar"); returns false;

// logging string "foo" at timestamp 10
logger.shouldPrintMessage(10,"foo"); returns false;

// logging string "foo" at timestamp 11
logger.shouldPrintMessage(11,"foo"); returns true;

Analysis:

I think this quiz is pretty straightforward. You need to implement a function that would return a boolean value to indicate if a message would need to send based on the criteria: if and only if it’s not printed in the last 10 seconds. You need to have a Map to record when a message has been sent. Let’s see how to do it.

class Logger {
    
  private HashMap<String, Integer> messages;

  /** Initialize your data structure here. */
  public Logger() {
    messages = new HashMap();
  }

  /** Returns true if the message should be printed in the given timestamp, otherwise returns false.
    If this method returns false, the message will not be printed.
    The timestamp is in seconds granularity. */
  public boolean shouldPrintMessage(int timestamp, String message) {
    if (messages.containsKey(message)) {
      if (messages.get(message) + 10 > timestamp) return false;
    }
    messages.put(message, timestamp);
    return true;
  }
}

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