# Construct an array from XOR of all elements of array except element at same index

Given an array A[] having n positive elements. The task to create another array B[] such as B[i] is XOR of all elements of array A[] except A[i].**Examples :**

Input : A[] = {2, 1, 5, 9} Output : B[] = {13, 14, 10, 6} Input : A[] = {2, 1, 3, 6} Output : B[] = {4, 7, 5, 0}

**Naive Approach : **

We can simple calculate B[i] as XOR of all elements of A[] except A[i], as

for (int i = 0; i < n; i++) { B[i] = 0; for (int j = 0; j < n; j++) if ( i != j) B[i] ^= A[j]; }

Time complexity for this naive approach is O (n^2).

Auxiliary Space for this naive approach is O (n).**Optimized Approach : **

First calculate XOR of all elements of array A[] say ‘xor’, and for each element of array A[] calculate **A[i] = xor ^ A[i] **.

int xor = 0; for (int i = 0; i < n; i++) xor ^= A[i]; for (int i = 0; i < n; i++) A[i] = xor ^ A[i];

Time complexity for this approach is O (n).

Auxiliary Space for this approach is O (1).

## C++

// C++ program to construct array from // XOR of elements of given array #include <bits/stdc++.h> using namespace std; // function to construct new array void constructXOR(int A[], int n) { // calculate xor of array int XOR = 0; for (int i = 0; i < n; i++) XOR ^= A[i]; // update array for (int i = 0; i < n; i++) A[i] = XOR ^ A[i]; } // Driver code int main() { int A[] = { 2, 4, 1, 3, 5}; int n = sizeof(A) / sizeof(A[0]); constructXOR(A, n); // print result for (int i = 0; i < n; i++) cout << A[i] << " "; return 0; }

## Java

// Java program to construct array from // XOR of elements of given array class GFG { // function to construct new array static void constructXOR(int A[], int n) { // calculate xor of array int XOR = 0; for (int i = 0; i < n; i++) XOR ^= A[i]; // update array for (int i = 0; i < n; i++) A[i] = XOR ^ A[i]; } // Driver code public static void main(String[] args) { int A[] = { 2, 4, 1, 3, 5}; int n = A.length; constructXOR(A, n); // print result for (int i = 0; i < n; i++) System.out.print(A[i] + " "); } } // This code is contributed by Anant Agarwal.

## Python3

# Python 3 program to construct # array from XOR of elements # of given array # function to construct new array def constructXOR(A, n): # calculate xor of array XOR = 0 for i in range(0, n): XOR ^= A[i] # update array for i in range(0, n): A[i] = XOR ^ A[i] # Driver code A = [ 2, 4, 1, 3, 5 ] n = len(A) constructXOR(A, n) # print result for i in range(0,n): print(A[i], end =" ") # This code is contributed by Smitha Dinesh Semwal

## C#

// C# program to construct array from // XOR of elements of given array using System; class GFG { // function to construct new array static void constructXOR(int []A, int n) { // calculate xor of array int XOR = 0; for (int i = 0; i < n; i++) XOR ^= A[i]; // update array for (int i = 0; i < n; i++) A[i] = XOR ^ A[i]; } // Driver code public static void Main() { int []A = { 2, 4, 1, 3, 5}; int n = A.Length; constructXOR(A, n); // print result for (int i = 0; i < n; i++) Console.Write(A[i] + " "); } } // This code is contributed by nitin mittal

## PHP

<?php // Program to construct array from // XOR of elements of given array // function to construct new array function constructXOR(&$A, $n) { // calculate xor of array $XOR = 0; for ($i = 0; $i < $n; $i++) $XOR ^= $A[$i]; // update array for ($i = 0; $i < $n; $i++) $A[$i] = $XOR ^ $A[$i]; } // Driver code $A = array( 2, 4, 1, 3, 5); $n = sizeof($A); constructXOR($A, $n); // print result for ($i = 0; $i < $n; $i++) echo $A[$i] ." "; // This code is contributed // by ChitraNayal ?>

## Javascript

<script> // JavaScript program to construct array from // XOR of elements of given array // function to construct new array function constructXOR(A, n) { // calculate xor of array let XOR = 0; for (let i = 0; i < n; i++) XOR ^= A[i]; // update array for (let i = 0; i < n; i++) A[i] = XOR ^ A[i]; } // Driver code let A = [ 2, 4, 1, 3, 5]; let n = A.length; constructXOR(A, n); // print result for (let i = 0; i < n; i++) document.write(A[i] + " "); // This code is contributed by Surbhi Tyagi. </script>

Output:

3 5 0 2 4

**Related Problem : **

A Product Array Puzzle

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