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898. Bitwise ORs of Subarrays

Given an integer array arr, return the number of distinct bitwise ORs of all the non-empty subarrays of arr.

The bitwise OR of a subarray is the bitwise OR of each integer in the subarray. The bitwise OR of a subarray of one integer is that integer.

A subarray is a contiguous non-empty sequence of elements within an array.

Example 1:

Input: arr = [0]
Output: 1
Explanation: There is only one possible result: 0.

Example 2:

Input: arr = [1,1,2]
Output: 3
Explanation: The possible subarrays are [1], [1], [2], [1, 1], [1, 2], [1, 1, 2].
These yield the results 1, 1, 2, 1, 3, 3.
There are 3 unique values, so the answer is 3.

Example 3:

Input: arr = [1,2,4]
Output: 6
Explanation: The possible results are 1, 2, 3, 4, 6, and 7.

Constraints:

  • 1 <= arr.length <= 5 * 104
  • 0 <= arr[i] <= 109

Solution:

题看不懂系列

class Solution {
    public int subarrayBitwiseORs(int[] arr) {
        Set<Integer> result = new HashSet<>();

        Set<Integer> cur = new HashSet<>();

        for (int x : arr){
            Set<Integer> next = new HashSet<>();

            next.add(x);

            for (int v : cur){
                next.add(v | x);
            }

            cur = next;

            result.addAll(cur);
        }

        return result.size();
    }
}
// TC: O(n)
// SC: O(n)