# XOR of all elements of array with set bits equal to K

Given an array of integers and a number K. The task is to find the XOR of only those elements of the array whose total set bits are equal to K.

Examples:

```Input : arr[] = {1, 22, 3, 10}, K=1
Output : 1
Elements with set bits equal to 1 is 1.
So, XOR is also 1.

Input : arr[] = {3, 4, 10, 5, 8}, K=2
Output : 12
```

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

Approach:

1. Initialize an empty vector.
2. Traverse the array form left to right and check the set bits of each element.
3. Use, C++ inbuilt function __builtin_popcount() to count setbits.
4. Push the elements with K setbits into the vector.
5. Finally find XOR of all the elements of the vector.

Below is the implementation of the above approach:

## C++

 `// C++ program to find Xor ` `// of all elements with set bits ` `// equal to K ` `#include ` `using` `namespace` `std; ` ` `  `// Function to find Xor ` `// of desired elements ` `int` `xorGivenSetBits(``int` `arr[], ``int` `n, ``int` `k) ` `{ ` `    ``// Initialize vector ` `    ``vector<``int``> v; ` ` `  `    ``for` `(``int` `i = 0; i < n; i++) { ` `        ``if` `(__builtin_popcount(arr[i]) == k) { ` `            ``// push required elements ` `            ``v.push_back(arr[i]); ` `        ``} ` `    ``} ` ` `  `    ``// Initialize result with first element of vector ` `    ``int` `result = v[0]; ` ` `  `    ``for` `(``int` `i = 1; i < v.size(); i++) ` `        ``result = result ^ v[i]; ` ` `  `    ``return` `result; ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``int` `arr[] = { 2, 13, 1, 19, 7 }; ` `    ``int` `n = ``sizeof``(arr) / ``sizeof``(arr[0]); ` `    ``int` `k = 3; ` ` `  `    ``cout << xorGivenSetBits(arr, n, k); ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java program to find Xor ` `// of all elements with set bits ` `// equal to K ` `import` `java.util.*; ` ` `  `class` `GFG ` `{ ` ` `  `    ``// Function to find Xor ` `    ``// of desired elements ` `    ``static` `int` `xorGivenSetBits(``int` `arr[],  ` `                                ``int` `n, ``int` `k) ` `    ``{ ` `        ``// Initialize vector ` `        ``Vector v = ``new` `Vector<>(); ` ` `  `        ``for` `(``int` `i = ``0``; i < n; i++)  ` `        ``{ ` `            ``if` `(Integer.bitCount(arr[i]) == k) ` `            ``{ ` `                ``// push required elements ` `                ``v.add(arr[i]); ` `            ``} ` `        ``} ` ` `  `        ``// Initialize result with first element of vector ` `        ``int` `result = v.get(``0``); ` ` `  `        ``for` `(``int` `i = ``1``; i < v.size(); i++)  ` `        ``{ ` `            ``result = result ^ v.get(i); ` `        ``} ` ` `  `        ``return` `result; ` `    ``} ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `main(String[] args)  ` `    ``{ ` `        ``int` `arr[] = {``2``, ``13``, ``1``, ``19``, ``7``}; ` `        ``int` `n = arr.length; ` `        ``int` `k = ``3``; ` `        ``System.out.println(xorGivenSetBits(arr, n, k)); ` `    ``} ` `} ` ` `  `// This code contributed by Rajput-Ji `

## Python3

 `# Python 3 program to find Xor of all  ` `# elements with set bits equal to K ` ` `  `# Function to find Xor of desired elements ` `def` `xorGivenSetBits(arr, n, k): ` `     `  `    ``# Initialize vector ` `    ``v ``=` `[] ` `    ``for` `i ``in` `range``(``0``, n, ``1``): ` `        ``if` `(``bin``(arr[i]).count(``'1'``) ``=``=` `k): ` `             `  `            ``# push required elements ` `            ``v.append(arr[i]) ` `         `  `    ``# Initialize result with first  ` `    ``# element of vector ` `    ``result ``=` `v[``0``] ` ` `  `    ``for` `i ``in` `range``(``1``, ``len``(v), ``1``): ` `        ``result ``=` `result ^ v[i] ` ` `  `    ``return` `result ` ` `  `# Driver code ` `if` `__name__ ``=``=` `'__main__'``: ` `    ``arr ``=` `[``2``, ``13``, ``1``, ``19``, ``7``] ` `    ``n ``=` `len``(arr) ` `    ``k ``=` `3` ` `  `    ``print``(xorGivenSetBits(arr, n, k)) ` ` `  `# This code is contributed by ` `# Surendra_Gangwar `

## C#

 `// C# program to find Xor ` `// of all elements with set bits ` `// equal to K ` `using` `System; ` `using` `System.Collections; ` `using` `System.Linq; ` ` `  `class` `GFG ` `{ ` `     `  `// Function to find Xor ` `// of desired elements ` `static` `int` `xorGivenSetBits(``int` `[]arr, ``int` `n, ``int` `k) ` `{ ` `    ``// Initialize vector ` `    ``ArrayList v=``new` `ArrayList(); ` ` `  `    ``for` `(``int` `i = 0; i < n; i++)  ` `    ``{ ` `        ``if` `(Convert.ToString(arr[i], 2).Count(c => c == ``'1'``) == k)  ` `        ``{ ` `            ``// push required elements ` `            ``v.Add(arr[i]); ` `        ``} ` `    ``} ` ` `  `    ``// Initialize result with first element of vector ` `    ``int` `result = (``int``)v[0]; ` ` `  `    ``for` `(``int` `i = 1; i < v.Count; i++) ` `        ``result = result ^ (``int``)v[i]; ` ` `  `    ``return` `result; ` `} ` ` `  `// Driver code ` `static` `void` `Main() ` `{ ` `    ``int` `[]arr = { 2, 13, 1, 19, 7 }; ` `    ``int` `n = arr.Length; ` `    ``int` `k = 3; ` ` `  `    ``Console.WriteLine(xorGivenSetBits(arr, n, k)); ` `} ` `} ` ` `  `// This code is contributed by mits `

Output:

```25
```

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