Count Mentions Per User

Medium

You receive an integer numberOfUsers representing the total number of users and an array events of size n x 3.

Each events[i] can be either of the following two types:

Message Event: ["MESSAGE", "timestamp i ", "mentions_string i "]
- This event indicates that a set of users was mentioned in a message at timestamp i.
- The mentions_string i string can contain one of the following tokens:
  - id<number>: where <number> is an integer in range [0,numberOfUsers - 1]. There can be multiple ids separated by a single whitespace and may contain duplicates. This can mention even the offline users.
  - ALL: mentions all users.
  - HERE: mentions all online users.
Offline Event: ["OFFLINE", "timestamp i ", "id i "]
- This event indicates that the user id i had become offline at timestamp i for 60 time units. The user will automatically be online again at time timestamp i + 60.

Produce an array mentions where mentions[i] represents the number of mentions the user with id i has across all MESSAGE events.

All users are initially online, and if a user goes offline or comes back online, their status change is processed before handling any message event that occurs at the same timestamp.

Note that a user can be mentioned multiple times in a single message event, and each mention should be counted separately.

Example 1

Input: numberOfUsers = 2, events = [["MESSAGE","10","id1 id0"],["OFFLINE","11","0"],["MESSAGE","71","HERE"]]

Output: [2,2]

Explanation: Initially, all users are online.

At timestamp 10, id1 and id0 are mentioned. mentions = [1,1]

At timestamp 11, id0 goes offline.

At timestamp 71, id0 comes back online and "HERE" is mentioned. mentions = [2,2]

Example 2

Input: numberOfUsers = 2, events = [["MESSAGE","10","id1 id0"],["OFFLINE","11","0"],["MESSAGE","12","ALL"]]

Output: [2,2]

Explanation: Initially, all users are online.

At timestamp 10, id1 and id0 are mentioned. mentions = [1,1]

At timestamp 11, id0 goes offline.

At timestamp 12, "ALL" is mentioned. This includes offline users, so both id0 and id1 are mentioned. mentions = [2,2]

Example 3

Input: numberOfUsers = 2, events = [["OFFLINE","10","0"],["MESSAGE","12","HERE"]]

Output: [0,1]

Explanation: Initially, all users are online.

At timestamp 10, id0 goes offline.

At timestamp 12, "HERE" is mentioned. Because id0 is still offline, they will not be mentioned. mentions = [0,1]

Constraints

1 <= numberOfUsers <= 100
1 <= events.length <= 100
events[i].length == 3
events[i][0] will be one of MESSAGE or OFFLINE.
1 <= int(events[i][1]) <= 10^5
The number of id<number> mentions in any "MESSAGE" event is between 1 and 100.
0 <= <number> <= numberOfUsers - 1
It is guaranteed that the user id referenced in the OFFLINE event is online at the time the event occurs.

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