Maximum xor Value Pair n an Array Without Using Tries

[Jayanti Vishnoi]

I am not understanding the implementation of the question in Blog(M) complexity can anyone please help me to understand the flow of the problem.

this is the implementaiton:

#include<bits/stdc++.h> 
using namespace std; 
  // Utility function to check number of elements 
// having set msb as of pattern 
int checkBit(int pattern, int arr[], int n) 
{ 
    int count = 0; 
    for (int i = 0; i < n; i++) 
        if ((pattern & arr[i]) == pattern) 
            count++; 
    return count; 
} 
  // Function for finding maximum and value pair 
int maxAND (int arr[], int n) 
{ 
    int res = 0, count; 
  
    // iterate over total of 30bits from msb to lsb 
    for (int bit = 31; bit >= 0; bit--) 
    { 
        // 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 |= (1 << bit);         
    } 
    return res; 
} 
 // Driver function 
int main() 
{ 
    int arr[] = {4, 8, 6, 2}; 
    int n = sizeof(arr)/sizeof(arr[0]); 
    cout << "Maximum AND Value = " << maxAND(arr,n); 
    return 0; 
}