Problem description:

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.

Example 1:

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Input
["Logger", "shouldPrintMessage", "shouldPrintMessage", "shouldPrintMessage", "shouldPrintMessage", "shouldPrintMessage", "shouldPrintMessage"]
[[], [1, "foo"], [2, "bar"], [3, "foo"], [8, "bar"], [10, "foo"], [11, "foo"]]
Output
[null, true, true, false, false, false, true]

Explanation
Logger logger = new Logger();
logger.shouldPrintMessage(1, "foo");  // return true, next allowed timestamp for "foo" is 1 + 10 = 11
logger.shouldPrintMessage(2, "bar");  // return true, next allowed timestamp for "bar" is 2 + 10 = 12
logger.shouldPrintMessage(3, "foo");  // 3 < 11, return false
logger.shouldPrintMessage(8, "bar");  // 8 < 12, return false
logger.shouldPrintMessage(10, "foo"); // 10 < 11, return false
logger.shouldPrintMessage(11, "foo"); // 11 >= 11, return true, next allowed timestamp for "foo" is 11 + 10 = 21

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:

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class Logger:
    def __init__(self):
        self.map = defaultdict(int)
        
    def shouldPrintMessage(self, timestamp: int, message: str) -> bool:
        if self.map[message] > timestamp:
            return False
        self.map[message] = timestamp + 10
        return True

Circular buffer

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class Logger:

    def __init__(self):
        self.ttl = [0 for _ in range(10)] # put time 
        self.msgbuffer = [set() for _ in range(10)]
        
    def shouldPrintMessage(self, timestamp: int, message: str) -> bool:
        idx = timestamp % 10
        if self.ttl[idx] != timestamp:
            self.msgbuffer[idx] = set()
            self.ttl[idx] = timestamp
        
        for i in range(len(self.ttl)):
            # print(self.ttl[i], self.msgbuffer[i])
            if timestamp - self.ttl[i] < 10:
                if message in self.msgbuffer[i]:
                    return False
        
        self.msgbuffer[idx].add(message)
        # print("-----")
        return True
        
        
        """
        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.
        """
# Your Logger object will be instantiated and called as such:
# obj = Logger()
# param_1 = obj.shouldPrintMessage(timestamp,message)

time complexity: $O()$
space complexity: $O()$
reference:
related problem: