359. Logger Rate Limiter

Logger Rate Limiter

Design a logger system that receive 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 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;

Credits:Special thanks to @memoryless for adding this problem and creating all test cases.

Solution

public class Logger {
    PriorityQueue<Log> queue;


    private class Log {
        String s;
        int time;

        public Log(String s, int time) {
            this.s = s;
            this.time = time;
        }
    }

    /** Initialize your data structure here. */
    public Logger() {
        queue = new PriorityQueue<>((a, b) -> a.time - b.time);
    }

    /** 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) {
        int minTime = timestamp - 10;
        while (!queue.isEmpty() && queue.peek().time <= minTime) {
            queue.poll();
        }

        List<Log> logList = new ArrayList<>(queue);
        for(Log log:logList) {
            if (log.s.equals(message)) {
                return false;
            }
        }
                queue.add(new Log(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);
 */