Hiring process8 levels
  1. 1 IQ Test
  2. 2 Additional Online Test (If Required)
  3. 3 Office Interview with Hiring Manager
  4. 4 Unpaid Test Task (Motivation Check)
  5. 5 Paid Test Task and Follow-Up Interview
  6. 6 Iterative Paid Test Tasks
  7. 7 Office Verification
  8. 8 Final Interview with the Founder

Problems > Vertices of the Hull > Editorial

Vertices of the Hull — Solution & Editorial

Back to the Problem

Andrew's monotone chain: sort points, build lower and upper hulls rejecting non-left turns (strict cross-product ≤ 0 removes collinear points). Count distinct hull vertices.

Complexity: O(N log N)

Watch out: Collinear points on the hull boundary: whether they count as vertices depends on the ≤ vs < in the turn test.