This is $O(N^3)$ because we compute the total happiness of some array of winners $O(N)$ times. Each computation requires $O(N)$ days, and on each day we go through all members in the list, and the list may have up to $O(N)$ people.

Note there are easier $O(N^3^)$ solutions, we showed this one because it is easier to get to the next step with it.

Note there are easier solutions for $11$ points, we showed this one because it is easier to get to the next step with it.

h2. $O(N^2^)$