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Maximum sum by adding numbers with same number of set bits
  • Difficulty Level : Easy
  • Last Updated : 05 Oct, 2018

Given an array of N numbers, the task is to find the maximum sum that can be obtained by adding numbers with the same number of set bits.

Examples:

Input: 32 3 7 5 27 28
Output: 34

Input: 2 3 8 5 6 7
Output: 14



Approach:

  • Traverse in the array and count the number of set bits for every element.
  • Initialize an array for 32 bits, assuming the number to have a maximum of 32 set bits.
  • Iterate in the array and add the array element to the position which indicates the number of set bits.
  • Traverse and find the maximum sum and return it.

Below is the implementation of the above approach:

C++




// C++ program to find maximum sum
// by adding numbers with same number of set bits
#include <bits/stdc++.h>
using namespace std;
  
// count the number of bits
// for each element of array
int bit_count(int n)
{
    int count = 0;
  
    // Count the number of set bits
    while (n) {
        count++;
  
        n = n & (n - 1);
    }
  
    return count;
}
  
// Function to return the
// the maximum sum
int maxsum(int arr[], int n)
{
    int bits[n];
  
    // Calculate the
    for (int i = 0; i < n; i++) {
        bits[i] = bit_count(arr[i]);
    }
  
    // Assuming the number to be
    // a maximum of 32 bits
    int sum[32] = { 0 };
  
    // Add the number to the
    // number of set bits
    for (int i = 0; i < n; i++) {
        sum[bits[i]] += arr[i];
    }
  
    int maximum = 0;
  
    // Find the maximum sum
    for (int i = 0; i < 32; i++) {
  
        maximum = max(sum[i], maximum);
    }
  
    return maximum;
}
  
// Driver code
int main()
{
  
    int arr[] = { 2, 3, 8, 5, 6, 7 };
    int n = sizeof(arr) / sizeof(arr[0]);
    cout << maxsum(arr, n);
  
    return 0;
}


Java




// Java program to find maximum sum
// by adding numbers with same number of set bits
  
class GFG
{
// count the number of bits
// for each element of array
static int bit_count(int n)
{
    int count = 0;
  
    // Count the number of set bits
    while (n>0)
    {
        count++;
  
        n = n & (n - 1);
    }
  
    return count;
}
  
// Function to return the
// the maximum sum
static int maxsum(int[] arr, int n)
{
    int[] bits=new int[n];
  
    // Calculate the
    for (int i = 0; i < n; i++) 
    {
        bits[i] = bit_count(arr[i]);
    }
  
    // Assuming the number to be
    // a maximum of 32 bits
    int[] sum=new int[32];
  
    // Add the number to the
    // number of set bits
    for (int i = 0; i < n; i++)
    {
        sum[bits[i]] += arr[i];
    }
  
    int maximum = 0;
  
    // Find the maximum sum
    for (int i = 0; i < 32; i++)
    {
  
        maximum = Math.max(sum[i], maximum);
    }
  
    return maximum;
}
  
// Driver code
public static void main (String[] args)
{
    int[] arr = { 2 ,3 , 8, 5, 6, 7 };
    int n = arr.length;
    System.out.println(maxsum(arr, n));
  
}
}
  
// This Code is contributed by mits


Python3




# Python3 program to find maximum
# sum by adding numbers with
# same number of set bits
  
# count the number of bits
# for each element of array
def bit_count(n):
    count = 0;
  
    # Count the number
    # of set bits
    while (n > 0):
        count += 1;
  
        n = n & (n - 1);
  
    return count;
  
# Function to return the
# the maximum sum
def maxsum(arr, n):
    bits = [0] * n;
  
    # Calculate the
    for i in range(n): 
        bits[i] = bit_count(arr[i]);
  
    # Assuming the number to be
    # a maximum of 32 bits
    sum = [0] * 32;
  
    # Add the number to the
    # number of set bits
    for i in range(n): 
        sum[bits[i]] += arr[i];
  
    maximum = 0;
  
    # Find the maximum sum
    for i in range(32):
  
        maximum = max(sum[i], maximum);
  
    return maximum;
  
# Driver code
arr = [ 2, 3, 8, 5, 6, 7 ];
n = len(arr);
print(maxsum(arr, n));
  
# This code is contributed by mits


C#




// C# program to find maximum 
// sum by adding numbers with 
// same number of set bits
using System;
  
class GFG
{
// count the number of bits
// for each element of array
static int bit_count(int n)
{
    int count = 0;
  
    // Count the number
    // of set bits
    while (n > 0)
    {
        count++;
  
        n = n & (n - 1);
    }
  
    return count;
}
  
// Function to return the
// the maximum sum
static int maxsum(int[] arr, int n)
{
    int[] bits = new int[n];
  
    // Calculate the
    for (int i = 0; i < n; i++) 
    {
        bits[i] = bit_count(arr[i]);
    }
  
    // Assuming the number to be
    // a maximum of 32 bits
    int[] sum = new int[32];
  
    // Add the number to the
    // number of set bits
    for (int i = 0; i < n; i++)
    {
        sum[bits[i]] += arr[i];
    }
  
    int maximum = 0;
  
    // Find the maximum sum
    for (int i = 0; i < 32; i++)
    {
        maximum = Math.Max(sum[i], maximum);
    }
  
    return maximum;
}
  
// Driver code
static void Main()
{
    int[] arr = { 2 ,3 , 8, 5, 6, 7 };
    int n = arr.Length;
    Console.WriteLine(maxsum(arr, n));
}
}
  
// This Code is contributed by mits


PHP




<?php
// PHP program to find maximum
// sum by adding numbers with
// same number of set bits
  
// count the number of bits
// for each element of array
function bit_count($n)
{
    $count = 0;
  
    // Count the number
    // of set bits
    while ($n)
    {
        $count++;
  
        $n = $n & ($n - 1);
    }
  
    return $count;
}
  
// Function to return the
// the maximum sum
function maxsum($arr, $n)
{
    $bits = array($n);
  
    // Calculate the
    for ($i = 0; $i < $n; $i++) 
    {
        $bits[$i] = bit_count($arr[$i]);
    }
  
    // Assuming the number to be
    // a maximum of 32 bits
    $sum = array_fill(0, 32, 0);
  
    // Add the number to the
    // number of set bits
    for ($i = 0; $i < $n; $i++) 
    {
        $sum[$bits[$i]] += $arr[$i];
    }
  
    $maximum = 0;
  
    // Find the maximum sum
    for ($i = 0; $i < 32; $i++)
    {
  
        $maximum = max($sum[$i],
                       $maximum);
    }
  
    return $maximum;
}
  
// Driver code
$arr = array( 2, 3, 8, 5, 6, 7 );
$n = sizeof($arr);
echo maxsum($arr, $n);
  
// This code is contributed by mits
?>


Output:

14

Time Complexity: O(N * 32)
Auxiliary Space: O(N)

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