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Find bitwise AND (&) of all possible sub-arrays
  • Difficulty Level : Medium
  • Last Updated : 19 May, 2021

Given an array A of size N where 1\leq N \leq 10^{5}. The task is to find the AND of all possible sub-arrays of A and then the AND of all these results.

Examples: 

Input : 1 2 3
Output : 0
All possible subarrays are 
{1}, {2}, {3}, {1, 2}, {2, 3} and {1, 2, 3}
ANDs of these subarrays are 1, 2, 3, 0, 2, 0.
AND of these ANDs is 0.

Input : 100 500 1000
Output : 96 

Approach:
The Naive solution is to find the AND of all the sub-arrays and then print the AND of their results. This will lead to O(N2) solution.

Optimal Solution: Using the properties of X\&X\&...\&X=X i:e it doesn’t matter how many times an element comes, its ANDing will be counted as one only. Thus, our problem is reduced to finding the AND of all the elements of the array only.

Below is the implementation of the above approach.



C++




// C++ program to find of all the sub-arrays
#include <bits/stdc++.h>
using namespace std;
 
// function to return AND of sub-arrays
int AND(int a[], int n)
{
    int ans = a[0];
    for (int i = 0; i < n; ++i)
        ans &= a[i]; 
    return ans;
}
 
// Driver program
int main()
{
    int a[] = { 1, 2, 3 };
 
    // size of the array
    int n = sizeof(a) / sizeof(a[0]);
 
    // print and of all subarrays
    cout << AND(a, n);
 
    return 0;
}

Java




//Java program to find of all the sub-arrays
public class GFG {
 
    //function to return AND of sub-arrays
    static int AND(int a[], int n)
    {
     int ans = a[0];
     for (int i = 0; i < n; ++i)
         ans &= a[i]; 
     return ans;
    }
 
    // Driver code
    public static void main(String[] args) {
     
        int a[] = { 1, 2, 3 };
 
         // size of the array
         int n = a.length;
 
         // print and of all subarrays
         System.out.println(AND(a, n));
    }
}

Python 3




# Python 3 Program  to find of all the sub-arrays
 
# function to return AND of sub-arrays
def AND(a, n) :
 
    ans = a[0]
    for i in range(n) :
        ans &= a[i]
         
    return ans
 
 
 
# Driver Code
if __name__ == "__main__" :
 
    a = [ 1, 2, 3]
 
    # size of the array
    n = len(a)
 
    # print and of all subarrays
    print(AND(a, n))
 
# This code is contributed by ANKITRAI1

C#




//C# program to find of all the sub-arrays 
 
using System;
 
public class GFG {
   
    //function to return AND of sub-arrays
    static int AND(int []a, int n)
    {
     int ans = a[0];
     for (int i = 0; i < n; ++i) 
         ans &= a[i];  
     return ans;
    }
   
    // Driver code
    public static void Main() {
       
        int []a = { 1, 2, 3 };
   
         // size of the array
         int n = a.Length;
   
         // print and of all subarrays
         Console.WriteLine(AND(a, n));
    }
}

PHP




<?php
// PHP program to find of
// all the sub-arrays
 
// function to return AND
// of sub-arrays
function ANDS(&$a, $n)
{
    $ans = $a[0];
    for ($i = 0; $i < $n; ++$i)
        $ans &= $a[$i];
    return $ans;
}
 
// Driver Code
$a = array( 1, 2, 3 );
 
// size of the array
$n = sizeof($a);
 
// print and of all subarrays
echo ANDS($a, $n);
 
// This code is contributed
// by Shivi_Aggarwal
?>

Javascript




<script>
//Javascript program to find of all the sub-arrays
     
    //function to return AND of sub-arrays
    function AND(a,n)
    {
        let ans = a[0];
     for (let i = 0; i < n; ++i)
         ans &= a[i]; 
     return ans;
    }
     
    // Driver code
    let a=[ 1, 2, 3 ];
    // size of the array
    let n = a.length;
    // print and of all subarrays
    document.write(AND(a, n));
     
 
 
// This code is contributed by rag2127
</script>

OUTPUT: 

0

Time Complexity: O(N)
 

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