359. 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;

思路: 用拿map来记录message -> timestamp关系, 如果message不在map里面,则添加到map里面,返回true; 如果在map里面,需要把这条message之前的记录时间跟当前的timestamp做差比较,如果在10s内则返回false, 如果大于10s,则更新下map里面的时间,返回true。

public class Logger {
    HashMap<String, Integer> map;

    /** Initialize your data structure here. */
    public Logger() {
        map = 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 (!map.containsKey(message)) {
            map.put(message, timestamp);
        } else {
            int recordTime = map.get(message); 
            if (timestamp - recordTime < 10) {
                return false;
            } else {
                map.put(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);
 */
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