# Find extra element in the second array

Given two arrays A[] and B[]. The second array B[] contains all the elements of A[] except for 1 extra element. The task is to find that extra element.

Examples:

Input: A[] = { 1, 2, 3 }, B[] = {1, 2, 3, 4}
Output: 4
Element 4 is not present in array

Input: A[] = {10, 15, 5}, B[] = {10, 100, 15, 5}
Output: 100

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Naive approach: Run nested loops and find the element in B[] which is not present in A[]. The time complexity of this approach will be O(n2).

Efficient approach: If all the elements of the A[] and B[] are XORed together then every element of A[] will give 0 with its occurrence in B[] and the extra element say X when XORed with 0 will give (X XOR 0) = X which is the result.

Below is the implementation of the above approach:

## C++

 `// C++ implementation of the approach ` `#include ` `using` `namespace` `std; ` ` `  `// Function to return the extra ` `// element in B[] ` `int` `extraElement(``int` `A[], ``int` `B[], ``int` `n) ` `{ ` ` `  `    ``// To store the result ` `    ``int` `ans = 0; ` ` `  `    ``// Find the XOR of all the element ` `    ``// of array A[] and array B[] ` `    ``for` `(``int` `i = 0; i < n; i++) ` `        ``ans ^= A[i]; ` `    ``for` `(``int` `i = 0; i < n + 1; i++) ` `        ``ans ^= B[i]; ` ` `  `    ``return` `ans; ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``int` `A[] = { 10, 15, 5 }; ` `    ``int` `B[] = { 10, 100, 15, 5 }; ` `    ``int` `n = ``sizeof``(A) / ``sizeof``(``int``); ` ` `  `    ``cout << extraElement(A, B, n); ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java implementation of the approach  ` `class` `GFG ` `{ ` `     `  `    ``// Function to return the extra  ` `    ``// element in B[]  ` `    ``static` `int` `extraElement(``int` `A[], ``int` `B[], ``int` `n)  ` `    ``{  ` `     `  `        ``// To store the result  ` `        ``int` `ans = ``0``;  ` `     `  `        ``// Find the XOR of all the element  ` `        ``// of array A[] and array B[]  ` `        ``for` `(``int` `i = ``0``; i < n; i++)  ` `            ``ans ^= A[i];  ` `        ``for` `(``int` `i = ``0``; i < n + ``1``; i++)  ` `            ``ans ^= B[i];  ` `     `  `        ``return` `ans;  ` `    ``}  ` `     `  `    ``// Driver code  ` `    ``public` `static` `void` `main (String[] args) ` `    ``{  ` `        ``int` `A[] = { ``10``, ``15``, ``5` `};  ` `        ``int` `B[] = { ``10``, ``100``, ``15``, ``5` `};  ` `        ``int` `n = A.length;  ` `     `  `        ``System.out.println(extraElement(A, B, n));  ` `    ``}  ` `} ` ` `  `// This code is contributed by kanugargng `

## Python3

 `# Python3 implementation of the approach ` `# Function to return the extra ` `# element in B[] ` `def` `extraElement(A, B, n): ` ` `  `    ``# To store the result ` `    ``ans ``=` `0``; ` ` `  `    ``# Find the XOR of all the element ` `    ``# of array A[] and array B[] ` `    ``for` `i ``in` `range``(n): ` `        ``ans ^``=` `A[i]; ` `    ``for` `i ``in` `range``(n ``+` `1``): ` `        ``ans ^``=` `B[i]; ` ` `  `    ``return` `ans; ` ` `  `# Driver code ` `A ``=` `[ ``10``, ``15``, ``5` `]; ` `B ``=` `[ ``10``, ``100``, ``15``, ``5` `]; ` `n ``=` `len``(A); ` ` `  `print``(extraElement(A, B, n)); ` ` `  `# This code is contributed by 29AjayKumar `

## C#

 `// C# implementation of the approach  ` `using` `System; ` `     `  `class` `GFG ` `{ ` `     `  `    ``// Function to return the extra  ` `    ``// element in B[]  ` `    ``static` `int` `extraElement(``int` `[]A,  ` `                            ``int` `[]B, ``int` `n)  ` `    ``{  ` `     `  `        ``// To store the result  ` `        ``int` `ans = 0;  ` `     `  `        ``// Find the XOR of all the element  ` `        ``// of array A[] and array B[]  ` `        ``for` `(``int` `i = 0; i < n; i++)  ` `            ``ans ^= A[i];  ` `        ``for` `(``int` `i = 0; i < n + 1; i++)  ` `            ``ans ^= B[i];  ` `     `  `        ``return` `ans;  ` `    ``}  ` `     `  `    ``// Driver code  ` `    ``public` `static` `void` `Main (String[] args) ` `    ``{  ` `        ``int` `[]A = { 10, 15, 5 };  ` `        ``int` `[]B = { 10, 100, 15, 5 };  ` `        ``int` `n = A.Length;  ` `     `  `        ``Console.WriteLine(extraElement(A, B, n));  ` `    ``}  ` `} ` ` `  `// This code is contributed by 29AjayKumar `

Output:

```100
```

Time Complexity: O(N)
Space Complexity: O(1)

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Improved By : kanugargng, 29AjayKumar