count-number-of-teams.cpp

// Time:  O(n^2)
// Space: O(1)

class Solution {
public:
    int numTeams(vector<int>& rating) {
        int result = 0;
        for (int i = 1; i < rating.size() - 1; ++i) {
            vector<int> less(2), greater(2);
            for (int j = 0; j < rating.size(); ++j) {
                if (rating[i] > rating[j]) {
                    ++less[i < j];
                }
                if (rating[i] < rating[j]) {
                    ++greater[i < j];
                }
            }
            result += less[0] * greater[1] + greater[0] * less[1];
        }
        return result;
    }
};