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Qn - Implement Router

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Implement Router

Question

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: <br /> <span class="example-io">["Router", "addPacket", "addPacket", "addPacket", "addPacket", "addPacket", "forwardPacket", "addPacket", "getCount"]<br /> [[3], [1, 4, 90], [2, 5, 90], [1, 4, 90], [3, 5, 95], [4, 5, 105], [], [5, 2, 110], [5, 100, 110]]</span> Output: <br /> [null, true, true, false, true, true, [2, 5, 90], true, 1]

Example 2

Input: <br /> <span class="example-io">["Router", "addPacket", "forwardPacket", "forwardPacket"]<br /> [[2], [7, 4, 90], [], []]</span> Output: <br /> [null, true, [7, 4, 90], []]

Constraints

  • 2 <= memoryLimit <= 10^5

  • 1 <= source, destination <= 2 * 10^5

  • 1 <= timestamp <= 10^9

  • 1 <= startTime <= endTime <= 10^9

  • At most 10^5 calls will be made to addPacket, forwardPacket, and getCount methods altogether.

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

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