#3583
Count Special Triplets
medium · 47.1% accepted · 550 likes · top 32%
array · hash table · counting
Description
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 = nums.length
- 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 large, return it modulo 109 + 7.
Solution