2419. Longest Subarray With Maximum Bitwise AND

You are given an integer array nums of size n.
Consider a non-empty subarray from nums that has the maximum possible bitwise AND.
- In other words, let k be the maximum value of the bitwise AND of any subarray of nums. Then, only subarrays with a bitwise AND equal to k should be considered.
Return the length of the longest such subarray.
The bitwise AND of an array is the bitwise AND of all the numbers in it.
A subarray is a contiguous sequence of elements within an array.

Example 1

Input: nums = [1,2,3,3,2,2]
Output: 2
Explanation:
The maximum possible bitwise AND of a subarray is 3.
The longest subarray with that value is [3,3], so we return 2.

Example 2

Input: nums = [1,2,3,4]
Output: 1
Explanation:
The maximum possible bitwise AND of a subarray is 4.
The longest subarray with that value is [4], so we return 1.

Method 1

【O(n) time | O(1) space】

package Leetcode.Array;

/**
 * @Author zhengxingxing
 * @Date 2025/07/30
 */
public class LongestSubarrayWithMaximumBitwiseAND {

    public static int longestSubarray(int[] nums) {
        // Step 1: Find the maximum value in the array.
        int maxVal = nums[0];
        for (int num : nums) {
            if (num > maxVal) {
                maxVal = num;
            }
        }

        // Step 2: Find the longest sequence of consecutive elements equal to maxVal.
        int maxLen = 0;   // To store the maximum length found.
        int currLen = 0;  // To store the current length of consecutive maxVal elements.

        for (int num : nums) {
            if (num == maxVal) {
                // If the current element equals maxVal, increment the current length.
                currLen++;
                // Update maxLen if the current sequence is longer.
                if (currLen > maxLen) {
                    maxLen = currLen;
                }
            } else {
                // If the current element is not maxVal, reset the current length.
                currLen = 0;
            }
        }
        // Return the length of the longest subarray found.
        return maxLen;
    }

    public static void main(String[] args) {
        // Example 1: The longest subarray with maximum bitwise AND is [3, 3], length is 2.
        int[] nums1 = {1, 2, 3, 3, 2, 2};
        // Example 2: The longest subarray with maximum bitwise AND is [4], length is 1.
        int[] nums2 = {1, 2, 3, 4};

        System.out.println(longestSubarray(nums1)); // Output: 2
        System.out.println(longestSubarray(nums2)); // Output: 1
    }
}

Method 1

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