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


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++

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// C++ program to find Xor
// of all elements with set bits
// equal to K
#include <bits/stdc++.h>
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;
}

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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

Output:

25


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Improved By : SURENDRA_GANGWAR