Find bitwise OR of all possible sub-arrays
Given an array A of size N where, 
. The task is to find the OR of all possible sub-arrays of A and then the OR of all these results.
Examples:
Input : 1 4 6
Output : 7
All possible subarrays are
{1}, {1, 4}, {4, 6} and {1, 4, 6}
ORs of these subarrays are 1, 5, 6
and 7. OR of these ORs is 7.
Input : 10 100 1000
Output : 1006
Approach: In SET 1 we have seen how to find bitwise AND of all possible subarrays. Similar approach is also aplicable here.
The Naive solution is to find the OR of all the sub-arrays and then output the OR of their results. This will lead to O(N2) solution.
Efficient Solution: Using the property that 
i:e it doesn’t matter how many times an element comes, it’s ORing will be counted as one only. Thus our problem boils down to finding the OR of all the elements of the array.
Below is the implementation of above approach.
C++
// C++ program to find OR of all the sub-arrays #include <bits/stdc++.h> using namespace std; // function to return OR of sub-arrays int OR(int a[], int n) { int ans = a[0]; for (int i = 1; i < n; ++i) ans |= a[i]; return ans; } // Driver program int main() { int a[] = { 1, 4, 6 }; int n = sizeof(a) / sizeof(a[0]); // print OR of all subarrays cout << OR(a, n); return 0; } |
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Java
// Java program to find OR of // all the sub-arrays class GFG { // function to return OR // of sub-arrays static int OR(int a[],int n) { int ans = a[0]; int i; for(i = 1; i < n; i++) { ans |= a[i]; } return ans; } // Driver Code public static void main(String args[]) { int a[] = { 1, 4, 6}; int n = a.length; // print OR of all subarrays System.out.println(OR(a, n)); } } // This code is contributed // by ANKITRAI1 |
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Python3
# Python3 program to find OR of all the sub-arrays # function to return OR of sub-arrays def OR(a, n): ans = a[0] for i in range(1,n): ans |= a[i] return ans # Driver Code if __name__=='__main__': a = [1, 4, 6] n = len(a) # print OR of all subarrays print(OR(a, n)) # This code is contributed # by Shashank_Sharma |
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C#
// C# program to find OR of // all the sub-arrays using System; class GFG { // function to return OR // of sub-arrays static int OR(int[] a, int n) { int ans = a[0]; int i; for(i = 1; i < n; i++) { ans |= a[i]; } return ans; } // Driver Code public static void Main() { int[] a = { 1, 4, 6}; int n = a.Length; // print OR of all subarrays Console.Write(OR(a, n)); } } // This code is contributed // by ChitraNayal |
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PHP
<?php // PHP program to find OR // of all the sub-arrays // function to return OR // of sub-arrays function O_R($a, $n) { $ans = $a[0]; for ($i = 1; $i < $n; ++$i) $ans |= $a[$i]; return $ans; } // Driver Code $a = array( 1, 4, 6 ); $n = count($a); // print OR of all subarrays echo O_R($a, $n); // This code is contributed // by inder_verma ?> |
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Output:
7
Time Complexity: O(N)
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