FastPrep
Problem · Design

Record Log

● MediumOptiverOA

Suppose you are responsible for building a log server that will receive a large number of logs. Each log will have a log ID and timestamp. We want to keep track of these logs, but due to storage limitations, we can only return up to m logs from the last hour when requested.

Complete the following functions:

  • recordLog(logId, timestamp): Records a new log entry.
    • Each log is represented as an object with a logId and timestamp. The logId is an identifier for each log and the timestamp is an integer in seconds representing when the log was sent.
    • Logs may be received out of order.
    • The log ID is not guaranteed to be unique - the same log ID can be used for different logs.
  • getLogs(): Returns a comma separated string of the latest m logs from the last hour ascending by timestamp. In the event of a timestamp tie, order from earliest received to latest.
    • Return a string of the form "logId1,logId2,logId3,logId4" where logId4 is the latest timestamp log and logId1 is the earliest timestamp log received < 1 hour before logId4's timestamp.
  • getLogCount(): Returns the total number of logs received < 1 hour from the most recently stored log timestamp. In the event more than m logs have been received, still return the full count of logs.

Examples
01 · Example 1
m = 100
q = 10
operations = ["RECORD 1 0", "RECORD 2 300", "GET_LOGS", "COUNT", "RECORD 3 1200", "RECORD 1 1800", "GET_LOGS", "COUNT", "RECORD 4 3900", "GET_LOGS"]
return = "1,2\n2\n1,2,3,1\n4\n3,1,4"

  • After the first two RECORD operations, the logs within the last hour are 1 and 2. GET_LOGS returns "1,2".
  • COUNT returns 2 since there are two logs within the last hour.
  • After two more RECORD operations, the logs within the last hour are 1, 2, 3, and 1. GET_LOGS returns "1,2,3,1".
  • COUNT returns 4 since there are four logs within the last hour.
  • After the last RECORD operation, the logs within the last hour are 3, 1, and 4. GET_LOGS returns "3,1,4".

Constraints
  • 1 ≤ m ≤ 1000
  • 1 ≤ q ≤ 10^6
  • logId is an integer
  • timestamp is an integer representing a timestamp in seconds
More Optiver problems
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public void recordLog(int logId, int timestamp) {
    // write your code here
}

public String getLogs() {
    // write your code here
}

public int getLogCount() {
    // write your code here
}
m100
q10
operations["RECORD 1 0", "RECORD 2 300", "GET_LOGS", "COUNT", "RECORD 3 1200", "RECORD 1 1800", "GET_LOGS", "COUNT", "RECORD 4 3900", "GET_LOGS"]
expected"1,2\n2\n1,2,3,1\n4\n3,1,4"
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