Change all even bits in a number to 0

Given a number, change all bits at even positions to 0.

Examples:

Input : 30
Output : 10
Binary representation of 11110. 
Bits at Even positions are highlighted. 
After making all of them 0, we get 01010

Input :  10
Output :  10

Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

Method 1 (Bit Traversal)

The idea is to traverse through all even bits. We accumulate all powers of 2 in a number to subtract. Finally we subtract the accumulated value from n to obtain the result.

C++

// C++ program to change even 
// bits to 0. 
#include<bits/stdc++.h> 
using namespace std; 
  
// Returns modified number with 
// all even bits 0. 
int changeEvenBits(int n) 
{ 
    // To store sum of bits 
    // at even positions. 
    int to_subtract = 0; 
  
    // To store bits to shift 
    int m = 0; 
  
    // One by one put all even 
    // bits to end 
    for (int x = n; x; x >>= 2) 
    { 
        // If current last bit 
        // is set, add it to ans 
        if (x & 1) 
           to_subtract += (1 << m); 
  
        // Next shift position 
        m += 2; 
    } 
  
    return n - to_subtract; 
} 
  
// Driver code 
int main() 
{ 
    int n = 30; 
    cout << changeEvenBits(n) << endl; 
  
    return 0; 
} 

Java

// Java program to change even 
// bits to 0. 
import java.util.*; 
class GFG 
{ 
// Returns modified number with 
// all even bits 0. 
static int changeEvenBits(int n) 
{ 
    // To store sum of bits 
    // at even positions. 
    int to_subtract = 0; 
  
    // To store bits to shift 
    int m = 0; 
  
    // One by one put all even 
    // bits to end 
    for (int x = n; x>0; x >>= 2) 
    { 
        // If current last bit 
        // is set, add it to ans 
        if ((x & 1) > 0) 
        to_subtract += (1 << m); 
  
        // Next shift position 
        m += 2; 
    } 
  
    return n - to_subtract; 
} 
  
// Driver code 
    public static void main(String[] args) 
    { 
    int n = 30; 
    System.out.println(changeEvenBits(n));  
    } 
} 
/* This code is contributed by Mr. Somesh Awasthi */

Python

# Python program to change even 
# bits to 0. 
  
# Returns modified number with 
# all even bits 0. 
def changeEvenBits(n): 
      
    # To store sum of bits 
    # at even positions. 
    to_subtract = 0
   
    # To store bits to shift 
    m = 0
   
    # One by one put all even 
    # bits to end 
    x = n 
    while(x): 
      
        # If current last bit 
        # is set, add it to ans 
        if (x & 1): 
           to_subtract += (1 << m) 
   
        # Next shift position 
        m += 2
        x >>= 2
   
    return n - to_subtract 
   
# Driver code 
n = 30
print changeEvenBits(n) 
  
# This code is contributed by Sachin Bisht 

C#

// C# program to change even 
// bits to 0. 
using System; 
  
class GFG { 
      
    // Returns modified number with 
    // all even bits 0. 
    static int changeEvenBits(int n) 
    { 
          
        // To store sum of bits 
        // at even positions. 
        int to_subtract = 0; 
      
        // To store bits to shift 
        int m = 0; 
      
        // One by one put all even 
        // bits to end 
        for (int x = n; x > 0; x >>= 2) 
        { 
              
            // If current last bit 
            // is set, add it to ans 
            if ((x & 1) > 0) 
            to_subtract += (1 << m); 
      
            // Next shift position 
            m += 2; 
        } 
      
        return n - to_subtract; 
    } 
      
    // Driver code 
    public static void Main() 
    { 
        int n = 30; 
          
        Console.Write(changeEvenBits(n));  
    } 
} 
  
// This code is contributed by nitin mittal. 

PHP

<?php 
// PHP program to change even 
// bits to 0. 
  
// Returns modified number with 
// all even bits 0. 
function changeEvenBits($n) 
{ 
      
    // To store sum of bits 
    // at even positions. 
    $to_subtract = 0; 
  
    // To store bits to shift 
    $m = 0; 
  
    // One by one put all even 
    // bits to end 
    for ($x = $n; $x; $x >>= 2) 
    { 
          
        // If current last bit 
        // is set, add it to ans 
        if ($x & 1) 
        $to_subtract += (1 << $m); 
  
        // Next shift position 
        $m += 2; 
    } 
  
    return $n - $to_subtract; 
} 
  
    // Driver code 
    $n = 30; 
    echo changeEvenBits($n) ; 
  
// This code is contributed by nitin mittal 
?> 

Output :

Method 2 (Bitmask)

C++

#include<bits/stdc++.h> 
using namespace std; 
  
int convertEvenBitToOne(int n) { 
    return (n & 0xaaaaaaaa); 
} 
  
int main() { 
   int n = 30; 
   cout << convertEvenBitToOne(n); 
   return 0; 
} 

Java

// Java program using Bitmask to  
// Change all even bits in a  
// number to 0 
import java.io.*; 
  
class GFG { 
  
    static int convertEvenBitToOne(int n) 
    { 
        return (n & 0xaaaaaaaa); 
    } 
  
    // Driver code 
    public static void main (String[] args) 
    { 
        int n = 30; 
        System.out.println(  
                    convertEvenBitToOne(n)); 
    } 
} 
  
// This code is contributed by anuj_67. 

Python

def convertEvenBitToOne(n): 
    return (n & 0xaaaaaaaa) 
  
# Driver code 
n = 30
print convertEvenBitToOne(n) 
  
# This code is contributed by Sachin Bisht 

C#

// C# program using Bitmask to  
// Change all even bits in a  
// number to 0 
using System; 
  
class GFG { 
  
    static long convertEvenBitToOne(int n) 
    { 
        return (n & 0xaaaaaaaa); 
    } 
  
    // Driver code 
    public static void Main () 
    { 
        int n = 30; 
        Console.WriteLine(  
                    convertEvenBitToOne(n)); 
    } 
} 
  
// This code is contributed by anuj_67. 

PHP

<?php 
// PHP program using Bitmask to  
// Change all even bits in a  
// number to 0 
  
function convertEvenBitToOne($n) 
{ 
    return ($n & 0xaaaaaaaa); 
} 
  
// Driver Code 
$n = 30; 
echo convertEvenBitToOne($n); 
  
// This code is contributed by anuj_67. 
?> 

Output :

This article is contributed by RISHABH RAJ JHA . If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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My Personal Notes

Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

C++

Java

Python

C#

PHP

C++

Java

Python

C#

PHP

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