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algorithm notes: leetcode#359 logger rate limiter

admin 11月 12, 2020 0

Problem

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:

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Logger logger = new Logger();
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

Use hash table to store (message, timestamp). When receiving a message, if it is not in the hash table, return true. If it is in the hash table, but difference between timestamps is larger than 10, return true. Otherwise, return false.

Soultion

Python implementation

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class :
    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.logs = dict()
    def shouldPrintMessage(self, timestamp, message):
        """
        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.
        :type timestamp: int
        :type message: str
        :rtype: bool
        """
        if message not in self.logs or timestamp - self.logs[message] >= 10:
            self.logs[message] = timestamp
            return True
        return False

Java implementation

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class  {
    /** Initialize your data structure here. */
    private Map<String, Integer> logs;
    
    public () {
        logs = 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(!logs.containsKey(message) || timestamp - logs.get(message) >= 10){
            logs.put(message, timestamp);
            return true;
        }
        return false;
    }
}
/**
 * Your Logger object will be instantiated and called as such:
 * Logger obj = new Logger();
 * boolean param_1 = obj.shouldPrintMessage(timestamp,message);
 */

359. Logger Rate Limiter
(中文版) 算法笔记: Leetcode#359 Logger Rate Limiter

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