Py3 C++ hashmap多項次公式解梯形問題Leetcode 3623 Count Number of Trapezoids I

Py3 CPP多項次公式解梯形問題Leetcode 3623  Count Number of Trapezoids I

數有幾個不同水平梯形，先用hash map數有相同y座標的點，再用多項次公式解題

[Py3解請進]

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To count the number of different horizontal trapezoids, first use a hash map to count points with the same y-coordinate, then use a quadratic formula to solve the problem.

[codes on Leetcode]https://leetcode.com/problems/count-number-of-trapezoids-i/solutions/7386316/geometry-hashmap41ms-beats-9763-by-anwen-6ye1/

class Solution:
    def countTrapezoids(self, points: List[List[int]]) -> int:
        freq=Counter(p[1] for p in points)
        Sum, c2=0, 0
        for f in freq.values():
            if f<=1: continue
            c=f*(f-1)//2
            Sum+=c
            c2+=c*c
        return (Sum*Sum-c2)//2%(10**9+7)