Leetcode #2401: Longest Nice Subarray

In this guide, we solve Leetcode #2401 Longest Nice Subarray in Python and focus on the core idea that makes the solution efficient.

You will see the intuition, the step-by-step method, and a clean Python implementation you can use in interviews.

Leetcode

Problem Statement

You are given an array nums consisting of positive integers. We call a subarray of nums nice if the bitwise AND of every pair of elements that are in different positions in the subarray is equal to 0.

Quick Facts

Difficulty: Medium
Premium: No
Tags: Bit Manipulation, Array, Sliding Window

Intuition

We are looking for a contiguous region that satisfies a constraint, which is a classic sliding-window signal.

Expanding and shrinking the window lets us maintain validity without restarting the scan.

Approach

Grow the window with a right pointer, and shrink from the left only when the constraint is violated.

Track the best window as you go to keep the solution linear.

Steps:

Expand the right end of the window.
While invalid, move the left end to restore constraints.
Update the best window found.

Example

Input: nums = [1,3,8,48,10]
Output: 3
Explanation: The longest nice subarray is [3,8,48]. This subarray satisfies the conditions:
- 3 AND 8 = 0.
- 3 AND 48 = 0.
- 8 AND 48 = 0.
It can be proven that no longer nice subarray can be obtained, so we return 3.

Python Solution

class Solution:
    def longestNiceSubarray(self, nums: List[int]) -> int:
        ans = mask = l = 0
        for r, x in enumerate(nums):
            while mask & x:
                mask ^= nums[l]
                l += 1
            mask |= x
            ans = max(ans, r - l + 1)
        return ans

Complexity

The time complexity is $O(n)$ , where $n$ is the length of the array $\textit{nums}$ . The space complexity is $O(1)$ .

Edge Cases and Pitfalls

Watch for boundary values, empty inputs, and duplicate values where applicable. If the problem involves ordering or constraints, confirm the invariant is preserved at every step.

Summary

This Python solution focuses on the essential structure of the problem and keeps the implementation interview-friendly while meeting the constraints.

Python Solution

class Solution:
    def longestNiceSubarray(self, nums: List[int]) -> int:
        ans = mask = l = 0
        for r, x in enumerate(nums):
            while mask & x:
                mask ^= nums[l]
                l += 1
            mask |= x
            ans = max(ans, r - l + 1)
        return ans

Leetcode #2401: Longest Nice Subarray

Problem Statement

Quick Facts

Intuition

Approach

Example

Python Solution

Complexity

Edge Cases and Pitfalls

Summary

Ace your next coding interview

Leetcode #2401: Longest Nice Subarray

Problem Statement

Quick Facts

Intuition

Approach

Example

Python Solution

Complexity

Edge Cases and Pitfalls

Summary

Ace your next coding interview