好久沒寫了
一開始沒看清楚 以為是任意的梯形
結果後來才看到是平行x軸
那就簡單很多了
但我就寫的 挺醜
def countTrapezoids(self, points: List[List[int]]) -> int:
cnt = defaultdict(int)
for pt in points:
cnt[pt[1]] += 1
sm = 0
mod = 10**9 + 7
for k, v in cnt.items():
sm = (sm + (v*(v-1)//2)) % mod
rets = 0
for k, v in cnt.items():
cur = (v*(v-1)//2)
rets = (rets + cur * (sm-cur)) % mod
sm -= cur
return rets