count_special_triplets.py (976B)
| # 3583. Count Special Triplets
from collections import Counter
"""
you are given an integer array 'nums'. a special triplet is defined as a
triplet of indices '(i, j, k)' such that '0 <= i < j < k < n' where 'n =
len(nums)', 'nums[i] == nums[j] 2', 'nums[k] == nums[j] 2'. return the
total number of special triplets in the array. since the answer may be very
large, return it modulo 10^9 + 7.
"""
class Solution(object):
def specialTriplets(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
left, right = Counter(), Counter()
ans, mod = 0, 10**9 + 7
for i in nums:
ans += right[i // 2] if i % 2 == 0 else 0
right[i] += left[i * 2]
left[i] += 1
return ans % mod
if __name__ == "__main__":
obj = Solution()
print(obj.specialTriplets(nums=[6, 3, 6]))
print(obj.specialTriplets(nums=[0, 1, 0, 0]))
print(obj.specialTriplets(nums=[8, 4, 2, 8, 4]))
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