Extract 'k' bits from a given position in a number.

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

Examples: 

Input : number = 171
             k = 5 
             p = 2
Output : The extracted number is 21
171 is represented as 10101011 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++ 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 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 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 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# 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 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
?>

<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

Time Complexity: O(1)

Auxiliary Space: O(1)