Time Complexity
Sorting the points has time complexity O(n log n). While it may seem that the time complexity of the loop is O(n2), because for each point it goes back to check if any of the previous points make a "right turn", it is actually O(n), because each point is considered at most twice in some sense. Each point can appear only once as a point in a "left turn" (because the algorithm advances to the next point after that), and as a point in a "right turn" (because the point is removed). The overall time complexity is therefore O(n log n), since the time to sort dominates the time to actually compute the convex hull.
Read more about this topic: Graham Scan
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