Dropbox Interview Question for Software Trainees

Country: United States

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The enabling logic should be straightforward provided that you have ample memory. You could use a hash map for the counters id -> (timestamp, count). If someone makes a request you check if there is an entry. If there isn't or if the timestamp in the entry is less than the current timestamp-X, add/replace it with (timestamp, 0). Otherwise, if the counter is less than Y, replace the entry with (timestamp, count+1). Otherwise, block the request. You will also want to limit the size of the map if the range of ids is too big by evicting old values. Different strategies could be used like having a priority queue timestamp -> id where the top element in the queue is the oldest. Before making checks against the hash map you could repeatedly pop elements off the queue if they are too old and remove the corresponding elements from the hash map.

- adr July 18, 2018 | Flag Reply

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