LeetCode Solutions
982. Triples with Bitwise AND Equal To Zero
Time: $O(n^2)$ Space: $O(2^{16}) = O(1)$
class Solution {
public:
int countTriplets(vector<int>& A) {
constexpr int kMax = 1 << 16;
int ans = 0;
vector<int> count(kMax); // {A[i] & A[j]: times}
for (const int a : A)
for (const int b : A)
++count[a & b];
for (const int a : A)
for (int i = 0; i < kMax; ++i)
if (!(a & i))
ans += count[i];
return ans;
}
};
class Solution {
public int countTriplets(int[] A) {
final int kMax = 1 << 16;
int ans = 0;
int[] count = new int[kMax]; // {A[i] & A[j]: times}
for (final int a : A)
for (final int b : A)
++count[a & b];
for (final int a : A)
for (int i = 0; i < kMax; ++i)
if ((a & i) == 0)
ans += count[i];
return ans;
}
}