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Extract ‘k’ bits from a given position in a number.

  • Difficulty Level : Medium
  • Last Updated : 26 May, 2021

How to extract ‘k’ bits from a given position ‘p’ in a number?

Examples: 

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Input : number = 171
             k = 5 
             p = 2
Output : The extracted number is 21
171 is represented as 0101011 in binary,
so, you should get only 10101 i.e. 21.

Input : number = 72
            k = 5 
            p = 1
Output : The extracted number is 8
72 is represented as 1001000 in binary,
so, you should get only 01000 i.e 8.
 

1) Right shift number by p-1. 
2) Do bit wise AND of k set bits with the modified number. We can get k set bits by doing (1 << k) – 1.



C++




// C++ program to extract k bits from a given
// position.
#include <bits/stdc++.h>
using namespace std;
 
// Function to extract k bits from p position
// and returns the extracted value as integer
int bitExtracted(int number, int k, int p)
{
    return (((1 << k) - 1) & (number >> (p - 1)));
}
 
// Driver code
int main()
{
    int number = 171, k = 5, p = 2;
    cout << "The extracted number is " <<
            bitExtracted(number, k, p);
             
    return 0;
}
 
// This code is contributed by importantly

C




// C program to extract k bits from a given
// position.
#include <stdio.h>
 
// Function to extract k bits from p position
// and returns the extracted value as integer
int bitExtracted(int number, int k, int p)
{
    return (((1 << k) - 1) & (number >> (p - 1)));
}
 
// Driver code
int main()
{
    int number = 171, k = 5, p = 2;
    printf("The extracted number is %d",
               bitExtracted(number, k, p));
    return 0;
}

Java




// Java program to extract k bits from a given
// position.
 
class GFG {
 
    // Function to extract k bits from p position
    // and returns the extracted value as integer
    static int bitExtracted(int number, int k, int p)
    {
        return (((1 << k) - 1) & (number >> (p - 1)));
    }
  
    // Driver code
    public static void main (String[] args) {
        int number = 171, k = 5, p = 2;
        System.out.println("The extracted number is "+
               bitExtracted(number, k, p));
    }
}

Python




# Python program to extract k bits from a given
# position.
 
# Function to extract k bits from p position
# and returns the extracted value as integer
def bitExtracted(number, k, p):  
    return ( ((1 << k) - 1)  &  (number >> (p-1) ) );
 
# number is from where 'k' bits are extracted
# from p position
number = 171
k = 5
p = 2
print "The extracted number is ", bitExtracted(number, k, p)

C#




// C# program to extract k bits from a given
// position.
using System;
 
class GFG {
  
    // Function to extract k bits from p position
    // and returns the extracted value as integer
    static int bitExtracted(int number, int k, int p)
    {
        return (((1 << k) - 1) & (number >> (p - 1)));
    }
   
    // Driver code
    public static void Main()
    {
        int number = 171, k = 5, p = 2;
         
        Console.WriteLine("The extracted number is "
                      + bitExtracted(number, k, p));
    }
}
 
//This code is contributed by Anant Agarwal.

PHP




<?php
//PHP program to extract
// k bits from a given
// position.
 
// Function to extract k
// bits from p position
// and returns the extracted
// value as integer
function bitExtracted($number, $k, $p)
{
    return (((1 << $k) - 1) &
           ($number >> ($p - 1)));
}
 
    // Driver Code
    $number = 171; $k = 5; $p = 2;
    echo "The extracted number is ",
          bitExtracted($number, $k, $p);
           
// This code is contributed by Ajit
?>

Javascript




<script>
// JavaScript program to extract k bits from a given
// position.
 
// Function to extract k bits from p position
// and returns the extracted value as integer
function bitExtracted(number, k, p)
{
    return (((1 << k) - 1) & (number >> (p - 1)));
}
 
// Driver code
 
    let number = 171, k = 5, p = 2;
    document.write("The extracted number is ",
            bitExtracted(number, k, p));
 
 
// This code is contributed by Manoj.
</script>

Output : 

The extracted number is 21

 

This article is contributed by Ujjwal Aryal. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
 




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