AND of Triples Zero
Given an array of integers nums, count the number of triples (i, j, k) where indices can repeat, such that nums[i] & nums[j] & nums[k] == 0.
Examples
Input: [2,1,3]
Output: 12
Input: [0,0,0]
Output: 27
Hints
For each possible pair `(i, j)`, compute the bitwise AND `nums[i] & nums[j]` and store the frequency of each result in a hash map. Then, for each `nums[k]`, check if `nums[k]` can form a triple with any of these AND results to make the final AND zero (i.e., `(nums[i] & nums[j]) & nums[k] == 0`).
Optimize the previous approach by precomputing all possible AND results of pairs and their frequencies. Then, for each `nums[k]`, iterate through the hash map and count how many pairs `(i, j)` satisfy `(pair_and & nums[k]) == 0`. Multiply this count by the frequency of `nums[k]` to account for all possible `k` values.
Further optimize by leveraging the fact that the AND operation is monotonic (i.e., `a & b <= a` and `a & b <= b`). Precompute all possible AND results of pairs and their frequencies, then use inclusion-exclusion or bitmask techniques to efficiently count the number of valid triples without iterating through all possible `k` values explicitly. This reduces the time complexity from O(n³) to O(n² + m * 2^b), where `m` is the number of unique AND results and `b` is the number of bits in the integers.
AND of Triples Zero
Given an array of integers nums, count the number of triples (i, j, k) where indices can repeat, such that nums[i] & nums[j] & nums[k] == 0.