187. Design Logger System With Message Timestamps

Design Logger System With Message Timestamps

Design a Logger system that receives a stream of messages with timestamps.

Each message should be printed only if the same message was not printed during the previous 10 seconds.

Given a timestamp and a message, return true if the message should be printed at that timestamp. Otherwise, return false.

Multiple messages may arrive at the same timestamp.

Constructor and Method Signatures

Logger()

Creates an empty logger system.

boolean shouldPrintMessage(int timestamp, String message)

Returns true if message should be printed at timestamp.
Returns false if the same message was already printed in the last 10 seconds.
If the method returns true, the message is considered printed at the given timestamp.
If the method returns false, the message is not printed and its last printed timestamp does not change.

Parameters

timestamp: The time when the message arrives, measured in seconds.
message: The message string received by the logger.

Return Value

Return true if the message should be printed.
Return false otherwise.

Printing Rule

A message can be printed at timestamp timestamp if either:

The message has never been printed before.
The message was last printed at time lastPrintedTime and timestamp - lastPrintedTime ≥ 10.

If timestamp - lastPrintedTime < 10, the message must not be printed.

Constraints

0 ≤ timestamp ≤ 10⁹
1 ≤ message.length() ≤ 100
message contains lowercase English letters only.
Calls to shouldPrintMessage are made with non-decreasing timestamps.
No parameter value will be null.

Examples

Example 1

Logger logger = new Logger()
logger.shouldPrintMessage(timestamp = 1, message = "apple")
Output: true
Explanation: "apple" has never been printed before, so it is printed.

logger.shouldPrintMessage(timestamp = 2, message = "banana")
Output: true
Explanation: "banana" has never been printed before, so it is printed.

logger.shouldPrintMessage(timestamp = 5, message = "apple")
Output: false
Explanation: "apple" was printed at timestamp 1, and only 4 seconds have passed.

logger.shouldPrintMessage(timestamp = 10, message = "apple")
Output: false
Explanation: "apple" was printed at timestamp 1, and only 9 seconds have passed.

logger.shouldPrintMessage(timestamp = 11, message = "apple")
Output: true
Explanation: "apple" was last printed at timestamp 1, and 10 seconds have passed.

Example 2

Logger logger = new Logger()
logger.shouldPrintMessage(timestamp = 3, message = "cat")
Output: true
Explanation: "cat" has not been printed before.

logger.shouldPrintMessage(timestamp = 3, message = "dog")
Output: true
Explanation: Multiple messages may arrive at the same timestamp, and "dog" has not been printed before.

logger.shouldPrintMessage(timestamp = 3, message = "cat")
Output: false
Explanation: "cat" was already printed at timestamp 3.

logger.shouldPrintMessage(timestamp = 13, message = "cat")
Output: true
Explanation: "cat" was last printed at timestamp 3, and exactly 10 seconds have passed.