Programming exercise

Count conversions by campaign

Build a function that takes a list of conversion events and returns the number of valid conversions per campaign. You have 45 minutes and may consult documentation. Write and run your code in your own editor, then paste it below.

• An event is valid if it has an eventId and a campaignId that are both strings and neither is empty or whitespace-only. Keep valid IDs exactly as supplied.
• Count each valid eventId once across the entire list. The first valid occurrence wins, even if another occurrence has a different campaign.
• Report how many events were invalid. Valid duplicates do not increase that count.
• Support up to one million events.

Example input

[
  {"eventId": "e1", "campaignId": "A"},
  {"eventId": "e2", "campaignId": "B"},
  {"eventId": "e1", "campaignId": "B"},
  {"eventId": "e3", "campaignId": ""},
  {"eventId": "e3", "campaignId": "A"}
]

Expected result

{"counts": {"A": 2, "B": 1}, "invalidCount": 1}