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

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++

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// 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;
}

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Java

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// 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 */

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Python

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# 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

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C#

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// 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.

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PHP

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<?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
?>

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Output :



10

 

Method 2 (Bitmask)

C++

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

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Java

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// 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.

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Python

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

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C#

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// 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.

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PHP

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<?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.
?>

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Output :

10

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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Improved By : nitin mittal, vt_m



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