Today I have done leetcode's October LeetCoding Challenge with cpp.

October LeetCoding Challenge 18

Description

Count Number of Maximum Bitwise-OR Subsets

Given an integer array nums, find the maximum possible bitwise OR of a subset of nums and return the number of different non-empty subsets with the maximum bitwise OR.

An array a is a subset of an array b if a can be obtained from b by deleting some (possibly zero) elements of b. Two subsets are considered different if the indices of the elements chosen are different.

The bitwise OR of an array a is equal to a[0] OR a[1] OR ... OR a[a.length - 1] (0-indexed).

Example 1:

Input: nums = [3,1]
Output: 2
Explanation: The maximum possible bitwise OR of a subset is 3. There are 2 subsets with a bitwise OR of 3:
- [3]
- [3,1]

Example 2:

Input: nums = [2,2,2]
Output: 7
Explanation: All non-empty subsets of [2,2,2] have a bitwise OR of 2. There are 23 - 1 = 7 total subsets.

Example 3:

Input: nums = [3,2,1,5]
Output: 6
Explanation: The maximum possible bitwise OR of a subset is 7. There are 6 subsets with a bitwise OR of 7:
- [3,5]
- [3,1,5]
- [3,2,5]
- [3,2,1,5]
- [2,5]
- [2,1,5]

Constraints:

• 1 <= nums.length <= 16
• 1 <= nums[i] <= 105

Solution

class Solution {
public:
  int countMaxOrSubsets(vector<int>& nums) {
    int target = accumulate(nums.begin(), nums.end(), 0, [](int p, int c) { return p | c;});
    int len = nums.size();
    int answer = 0;
    for(int i = 1; i < (1 << len); ++i) {
      int current = 0;
      for(int b = 0; b < len; ++b) {
        if(i & (1 << b)) current |= nums[b];
      }
      if(current == target) answer += 1;
    }
    return answer;
  }
};