Product of count of set bits present in binary representations of elements in an array

Last Updated : 20 May, 2021
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Given an array arr[] consisting of N integers, the task is to find the product of the count of set bits in the binary representation of every array element.

Examples:

Input: arr[] = {3, 2, 4, 1, 5}
Output: 4
Explanation:
Binary representation of the array elements are {3, 2, 4, 1, 5} are {"11", "10", "100", "1", "101"} respectively.
Therefore, the product of count of set bits = (2 * 1 * 1 * 1 * 2) = 4.

Input: arr[] = {10, 11, 12}
Output: 12

Approach: The given problem can be solved by counting the total bits in the binary representation of every array element. Follow the steps below to solve the problem:

  • Initialize a variable, say product, to store the resultant product.
  • Traverse the given array arr[] and perform the following steps:
  • After completing the above steps, print the value of the product as the result.

Below is the implementation of the above approach:

C++ 
// C++ program for the above approach

#include <bits/stdc++.h>
using namespace std;

// Function to count the
// set bits in an integer
int countbits(int n)
{
    // Stores the count of set bits
    int count = 0;

    // Iterate while N is not equal to 0
    while (n != 0) {

        // Increment count by 1
        if (n & 1)
            count++;

        // Divide N by 2
        n = n / 2;
    }

    // Return the total count obtained
    return count;
}

// Function to find the product
// of count of set bits present
// in each element of an array
int BitProduct(int arr[], int N)
{
    // Stores the resultant product
    int product = 1;

    // Traverse the array arr[]
    for (int i = 0; i < N; i++) {

        // Stores the count
        // of set bits of arr[i]
        int bits = countbits(arr[i]);

        // Update the product
        product *= bits;
    }

    // Return the resultant product
    return product;
}

// Driver Code
int main()
{
    int arr[] = { 3, 2, 4, 1, 5 };
    int N = sizeof(arr) / sizeof(arr[0]);
    cout << BitProduct(arr, N);

    return 0;
}
Java 
// java program for the above approach
import java.io.*;
import java.lang.*;
import java.util.*;

public class GFG {

    // Function to count the
    // set bits in an integer
    static int countbits(int n)
    {
        // Stores the count of set bits
        int count = 0;

        // Iterate while N is not equal to 0
        while (n != 0) {

            // Increment count by 1
            if ((n & 1) != 0)
                count++;

            // Divide N by 2
            n = n / 2;
        }

        // Return the total count obtained
        return count;
    }

    // Function to find the product
    // of count of set bits present
    // in each element of an array
    static int BitProduct(int arr[], int N)
    {
      
        // Stores the resultant product
        int product = 1;

        // Traverse the array arr[]
        for (int i = 0; i < N; i++) {

            // Stores the count
            // of set bits of arr[i]
            int bits = countbits(arr[i]);

            // Update the product
            product *= bits;
        }

        // Return the resultant product
        return product;
    }

    // Driver Code
    public static void main(String[] args)
    {
        int arr[] = { 3, 2, 4, 1, 5 };
        int N = arr.length;
        System.out.print(BitProduct(arr, N));
    }
}

// This code is contributed by Kingash.
Python3 
# Python3 program for the above approach

# Function to count the
# set bits in an integer
def countbits(n):
  
    # Stores the count of set bits
    count = 0

    # Iterate while N is not equal to 0
    while (n != 0):

        # Increment count by 1
        if (n & 1):
            count += 1

        # Divide N by 2
        n = n // 2

    # Return the total count obtained
    return count

# Function to find the product
# of count of set bits present
# in each element of an array
def BitProduct(arr, N):
  
    # Stores the resultant product
    product = 1

    # Traverse the array arr[]
    for i in range(N):
      
        # Stores the count
        # of set bits of arr[i]
        bits = countbits(arr[i])

        # Update the product
        product *= bits

    # Return the resultant product
    return product

# Driver Code
if __name__ == '__main__':
    arr = [3, 2, 4, 1, 5]
    N = len(arr)
    print(BitProduct(arr, N))

    # This code is contributed by mohit kumar 29.
C# 
// C# program for the above approach
using System;

public class GFG {

    // Function to count the
    // set bits in an integer
    static int countbits(int n)
    {
        // Stores the count of set bits
        int count = 0;

        // Iterate while N is not equal to 0
        while (n != 0) {

            // Increment count by 1
            if ((n & 1) != 0)
                count++;

            // Divide N by 2
            n = n / 2;
        }

        // Return the total count obtained
        return count;
    }

    // Function to find the product
    // of count of set bits present
    // in each element of an array
    static int BitProduct(int[] arr, int N)
    {

        // Stores the resultant product
        int product = 1;

        // Traverse the array arr[]
        for (int i = 0; i < N; i++) {

            // Stores the count
            // of set bits of arr[i]
            int bits = countbits(arr[i]);

            // Update the product
            product *= bits;
        }

        // Return the resultant product
        return product;
    }

    // Driver Code
    public static void Main(string[] args)
    {
        int[] arr = { 3, 2, 4, 1, 5 };
        int N = arr.Length;
        Console.Write(BitProduct(arr, N));
    }
}

// This code is contributed by ukasp.
JavaScript 
<script>

// Javascript program for the above approach


// Function to count the
// set bits in an integer
function countbits( n)
{
    // Stores the count of set bits
    let count = 0;

    // Iterate while N is not equal to 0
    while (n != 0) {

        // Increment count by 1
        if ((n & 1) != 0)
            count++;

        // Divide N by 2
        n = Math.floor(n / 2);
        }

    // Return the total count obtained
    return count;
}

// Function to find the product
// of count of set bits present
// in each element of an array
function BitProduct( arr, N)
{

    // Stores the resultant product
    let product = 1;

    // Traverse the array arr[]
    for (let i = 0; i < N; i++) {

        // Stores the count
        // of set bits of arr[i]
        let bits = countbits(arr[i]);

        // Update the product
        product *= bits;
    }

    // Return the resultant product
    return product;
}


// Driver Code

let arr = [ 3, 2, 4, 1, 5 ];
let N = arr.length;
document.write(BitProduct(arr, N));

</script>

Output: 
4

 

Time Complexity: O(N * log M), M is the maximum element of the array.
Auxiliary Space: O(1)


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Count pairs of elements such that number of set bits in their AND is B[i]

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