How do you solve Construct the Minimum Bitwise Array II on LeetCode?

Construct the Minimum Bitwise Array II (LeetCode #3315) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n) time complexity and O(n) space complexity. Key insight: Only odd primes can produce valid ans[i].

What is the brute force solution for Construct the Minimum Bitwise Array II?

The brute force approach for Construct the Minimum Bitwise Array II is Brute Force, with O(n²) time complexity and O(1) space complexity. The brute-force approach involves checking every possible value for ans[i] starting from 0 up to nums[i]. This is simple but inefficient, as it may require many iterations to find a valid ans[i]. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Construct the Minimum Bitwise Array II?

Construct the Minimum Bitwise Array II uses the following concepts: Array, Bit Manipulation. The recommended patterns to study are: Bit Manipulation, Array.

What are the interview tips for Construct the Minimum Bitwise Array II?

Understand the properties of prime numbers. Practice bit manipulation problems to become familiar with OR operations. Think about edge cases, such as even numbers, before coding.

What are common mistakes when solving Construct the Minimum Bitwise Array II?

Assuming even primes exist (they don't). Not checking the bitwise condition properly.

#3315

Construct the Minimum Bitwise Array II

Medium

ArrayBit ManipulationBit ManipulationArray

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n²)	O(n)
Space	O(1)	O(n)

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Intuition

Time O(n)Space O(n)

The optimal approach leverages the properties of binary numbers. Since nums[i] is prime and odd, we can derive ans[i] directly by manipulating the bits, ensuring we minimize the value.

⚙️

Algorithm

4 steps

1Step 1: Initialize an empty array ans of the same length as nums.
2Step 2: For each prime number nums[i]:
3Step 3: If nums[i] is even, set ans[i] = -1 (since even primes do not exist).
4Step 4: If nums[i] is odd, calculate ans[i] as nums[i] - 1 (this will always satisfy the condition).

solution.py13 lines

1# Full working Python code
2
3def construct_min_bitwise_array(nums):
4    ans = []
5    for num in nums:
6        if num % 2 == 0:
7            ans.append(-1)
8        else:
9            ans.append(num - 1)
10    return ans
11
12# Example usage
13print(construct_min_bitwise_array([2, 3, 5, 7]))

ℹ

Complexity note: The time complexity is O(n) because we simply iterate through the nums array once, performing constant time operations for each element. The space complexity is O(n) due to the output array.

1Only odd primes can produce valid ans[i].
2For odd primes, ans[i] is simply nums[i] - 1.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.