Find the absolute difference of set bits at even and odd indices of N

Given an integer N, the task is to find the absolute difference of set bits at even and odd indices of number N. (0-based Indexing)

Examples: 

Input: N = 15
Output: 0
Explanation: The binary representation of 15 is 1111. So, it contains 1 on the 1st and 3rd position and it contains 1 on the 0th and 2nd position. Therefore, the difference between even and odd bits is 2 – 2 which is 0.

Input: N = 17
Output: 2
Explanation: The binary representation of 17 is 10001. So, it contains 1 on the 0th and 4th positions. Therefore, the difference between even and odd bits is 2-0 which is 2.

Approach: This can be solved with the following idea:

Form a binary string of a given number N and start iterating from the right end, maintaining the sum of numbers present at even and odd indexes separately. 

Below are the steps involved in the implementation of the code:

• Calculate the length of the binary representation of the number.
• Iterating through each bit position, checking if it is even or odd
• At last, Count the number of set bits accordingly using bitwise operations. 
• Return the absolute difference between even and odd bits.

Below is the implementation of the code:

C++

// C++ implementation of code
#include <bits/stdc++.h>
using namespace std;

// Function to find absolute difference
int diffEvenOddBit(int n)
{

    int count1 = 0;
    int count2 = 0;
    int m = n;
    int len = 0;

    // Count the length of binary string
    while (m) {
        len++;
        m = m >> 1;
    }

    for (int i = 0; i < len; i++) {

        // Check for 1 at even index
        if (i % 2 == 0) {
            if (n & 1 << i) {
                count1++;
            }
        }

        // Check for 1 at odd index
        else {
            if (n & 1 << i) {
                count2++;
            }
        }
    }

    // Difference of even and odd bits
    int diff = count1 - count2;
    return diff;
}

// Driver code
int main()
{

    int n = 17;

    // Function call
    cout << diffEvenOddBit(n) << " ";
    return 0;
}

Java

import java.io.*;

public class Main {

    // Function to find absolute difference
    static int diffEvenOddBit(int n)
    {

        int count1 = 0;
        int count2 = 0;
        int m = n;
        int len = 0;

        // Count the length of binary string
        while (m > 0) {
            len++;
            m = m >> 1;
        }

        for (int i = 0; i < len; i++) {

            // Check for 1 at even index
            if (i % 2 == 0) {
                if ((n & (1 << i)) != 0) {
                    count1++;
                }
            }

            // Check for 1 at odd index
            else {
                if ((n & (1 << i)) != 0) {
                    count2++;
                }
            }
        }

        // Difference of even and odd bits
        int diff = count1 - count2;
        return diff;
    }

    // Driver code
    public static void main(String[] args)
    {

        int n = 17;

        // Function call
        System.out.print(diffEvenOddBit(n) + " ");
    }
}

Python3

# Function to find absolute difference
def diffEvenOddBit(n):
    count1 = 0
    count2 = 0
    m = n
    len = 0

    # Count the length of binary string
    while m:
        len += 1
        m = m >> 1

    for i in range(len):
        # Check for 1 at even index
        if i % 2 == 0:
            if n & (1 << i):
                count1 += 1

        # Check for 1 at odd index
        else:
            if n & (1 << i):
                count2 += 1

    # Difference of even and odd bits
    diff = count1 - count2
    return abs(diff)

# Driver code
n = 17

# Function call
print(diffEvenOddBit(n))

C#

using System;
class GFG
{
    // Function to find absolute difference
    static int DiffEvenOddBit(int n)
    {
        int count1 = 0;
        int count2 = 0;
        int m = n;
        int len = 0;
        // Count the length of the binary string
        while (m != 0)
        {
            len++;
            m = m >> 1;
        }
        for (int i = 0; i < len; i++)
        {
            // Check for 1 at even index
            if (i % 2 == 0)
            {
                if ((n & (1 << i)) != 0)
                {
                    count1++;
                }
            }
            // Check for 1
            else
            {
                if ((n & (1 << i)) != 0)
                {
                    count2++;
                }
            }
        }
        // Difference even and odd bits
        int diff = count1 - count2;
        return diff;
    }
    static void Main(string[] args)
    {
        int n = 17;
        // Function call
        Console.WriteLine(DiffEvenOddBit(n));
    }
}

Javascript

// Function to find absolute difference
function diffEvenOddBit(n) {
  let count1 = 0;
  let count2 = 0;
  let m = n;
  let len = 0;

  // Count the length of binary string
  while (m) {
    len++;
    m = m >> 1;
  }

  for (let i = 0; i < len; i++) {
    // Check for 1 at even index
    if (i % 2 === 0) {
      if (n & (1 << i)) {
        count1++;
      }
    }
    // Check for 1 at odd index
    else {
      if (n & (1 << i)) {
        count2++;
      }
    }
  }

  // Difference of even and odd bits
  const diff = count1 - count2;
  return diff;
}

// Driver code
const n = 17;

// Function call
console.log(diffEvenOddBit(n));


//This code is contributed by Tushar Rokade

Output

2 

Time Complexity: O(logn)
Auxiliary Space: O(1)Related Articles: