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.

solution

The only intuition required here is that the bitwise AND of two numbers will always be $\le$ the bigger of the two values.

So, this question is really just asking for the longest block of the maximum value in the array (because the biggest bitwise AND will always consist of just the maximum value of the array).

def longestSubarray(self, nums: List[int]) -> int:
	res = 1
	best = nums[0]
	prev = nums[0]
	count = 1
	  
	for num in nums[1:]:
		if num == prev:
			count += 1
	  
			if num == best:
				res = max(res, count)
 
		else:
			if num > best:
				best = num
				res = 1
			prev = num
			count = 1
 
	return res