Maximum AND value

Given an array of N positive elements, the task is to find the maximum AND value generated by any pair of elements from the array.

loop_invariant

• initialization_phase iterate for 32 bits starting from 31 to -1 in reverse order. Initialize and assign 0 value to res variable.
• most_significant_bit andleast_significant_bit
• create a check bit function to check number having set msb.

bit_manupulation

# Python3 Program to find maximum XOR
# value of a pair
 
# Utility function to check number of
# elements having set msb as of pattern
 
 
def checkBit(pattern, arr, n):
	count = 0
 
	for i in range(0, n):
		if ((pattern & arr[i]) == pattern):
			count = count + 1
	return count
 
# Function for finding maximum and
# value pair
 
 
def maxAND(arr, n):
	res = 0
 
	# iterate over total of 32bits
	# from msb to lsb
	for bit in range(31, -1, -1):
 
		# find the count of element
		# having set msb
		count = checkBit(res | (1 << bit), arr, n)
 
		# if count >= 2 set particular
		# bit in result
		if (count >= 2):
			res = res | (1 << bit)
 
	return res
 
 
# Driver function
arr = [4, 8, 6, 2]
n = len(arr)
print("Maximum AND Value = ", maxAND(arr, n))