3508 - Implement Router.

Medium

Design a data structure that can efficiently manage data packets in a network router. Each data packet consists of the following attributes:

• source: A unique identifier for the machine that generated the packet.

• destination: A unique identifier for the target machine.

• timestamp: The time at which the packet arrived at the router.

Implement the Router class:

Router(int memoryLimit): Initializes the Router object with a fixed memory limit.

• memoryLimit is the maximum number of packets the router can store at any given time.

• If adding a new packet would exceed this limit, the oldest packet must be removed to free up space.

bool addPacket(int source, int destination, int timestamp): Adds a packet with the given attributes to the router.

• A packet is considered a duplicate if another packet with the same source, destination, and timestamp already exists in the router.

• Return true if the packet is successfully added (i.e., it is not a duplicate); otherwise return false.

int[] forwardPacket(): Forwards the next packet in FIFO (First In First Out) order.

• Remove the packet from storage.

• Return the packet as an array [source, destination, timestamp].

• If there are no packets to forward, return an empty array.

int getCount(int destination, int startTime, int endTime):

• Returns the number of packets currently stored in the router (i.e., not yet forwarded) that have the specified destination and have timestamps in the inclusive range [startTime, endTime].

Note that queries for addPacket will be made in increasing order of timestamp.

Example 1:

Input: "Router", "addPacket", "addPacket", "addPacket", "addPacket", "addPacket", "forwardPacket", "addPacket", "getCount" [3, 1, 4, 90, 2, 5, 90, 1, 4, 90, 3, 5, 95, 4, 5, 105, [], 5, 2, 110, 5, 100, 110]

Output: [null, true, true, false, true, true, 2, 5, 90, true, 1]

Explanation

Router router = new Router(3); // Initialize Router with memoryLimit of 3. router.addPacket(1, 4, 90); // Packet is added. Return True. router.addPacket(2, 5, 90); // Packet is added. Return True. router.addPacket(1, 4, 90); // This is a duplicate packet. Return False. router.addPacket(3, 5, 95); // Packet is added. Return True router.addPacket(4, 5, 105); // Packet is added, [1, 4, 90] is removed as number of packets exceeds memoryLimit. Return True. router.forwardPacket(); // Return [2, 5, 90] and remove it from router. router.addPacket(5, 2, 110); // Packet is added. Return True. router.getCount(5, 100, 110); // The only packet with destination 5 and timestamp in the inclusive range [100, 110] is [4, 5, 105]. Return 1.

Example 2:

Input: "Router", "addPacket", "forwardPacket", "forwardPacket" [2, 7, 4, 90, [], []]

Output: [null, true, 7, 4, 90, []]

Explanation

Router router = new Router(2); // Initialize Router with memoryLimit of 2. router.addPacket(7, 4, 90); // Return True. router.forwardPacket(); // Return [7, 4, 90]. router.forwardPacket(); // There are no packets left, return [].

Constraints:

• <code>2 <= memoryLimit <= 10⁵</code>

• <code>1 <= source, destination <= 2 * 10⁵</code>

• <code>1 <= timestamp <= 10⁹</code>

• <code>1 <= startTime <= endTime <= 10⁹</code>

• At most <code>10⁵</code> calls will be made to addPacket, forwardPacket, and getCount methods altogether.

• queries for addPacket will be made in increasing order of timestamp.