2025-12-02 19:36:01 +0300 MSK

class Solution:
    def countTrapezoids(self, points: List[List[int]]) -> int:
        point_num = defaultdict(int)
        mod = 10**9 + 7
        ans, total_sum = 0, 0
        for point in points:
            point_num[point[1]] += 1
        for p_num in point_num.values():
            edge = p_num * (p_num - 1) // 2
            ans = (ans + edge * total_sum) % mod
            total_sum = (total_sum + edge) % mod
        return ans