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Check whether K-th bit is set or not
  • Difficulty Level : Easy
  • Last Updated : 23 Apr, 2021

Given a number n, check if the Kth bit of n is set or not.
 

Examples: 

Input : n = 5, k = 1
Output : SET
5 is represented as 101 in binary and has its first bit set.

Input : n = 2, k = 3
Output : NOT SET
2 is represented as 10 in binary, all higher i.e. beyond MSB, bits are NOT SET.

Method 1 (Using Left Shift Operator) 
Below are simple steps to find the value of Kth bit: 

1) Left shift given number 1 by k-1 to create a number that has only set bit as k-th bit.
   temp = 1 << (k-1)
2) If bitwise AND of n and temp is non-zero, then result is SET else result is NOT SET.

Example: 

 n = 75 and k = 4
 temp = 1 << (k-1) = 1 << 3 = 8 
 Binary Representation of temp = 0..00001000 
 Binary Representation of n = 0..01001011 
 Since bitwise AND of n and temp is non-zero, result is SET.

C++




// CPP program to check if k-th bit
// of a given number is set or not
#include <iostream>
using namespace std;
 
void isKthBitSet(int n, int k)
{
    if (n & (1 << (k - 1)))
        cout << "SET";
    else
        cout << "NOT SET";
}
 
// Driver code
int main()
{
    int n = 5, k = 1;
    isKthBitSet(n, k);
    return 0;
}

Java




// Java program to check if k-th bit
// of a given number is set or not
 
class Number {
    public static void isKthBitSet(int n,
                                   int k)
    {
        if ((n & (1 << (k - 1))) > 0)
            System.out.print("SET");
        else
            System.out.print("NOT SET");
    }
 
    // driver code
    public static void main(String[] args)
    {
        int n = 5, k = 1;
        isKthBitSet(n, k);
    }
}
 
// This code is contributed by rishabh_jain

Python3




# Python3 code to check if k-th bit
# of a given number is set or not
 
def isKthBitSet(n, k):
    if n & (1 << (k - 1)):
        print( "SET")
    else:
        print("NOT SET")
 
# Driver code
n = 5
k = 1
isKthBitSet(n, k)
 
# This code is contributed by "Sharad_Bhardwaj".

C#




// C# program to check if k-th bit
// of a given number is set or not.
using System;
 
class GFG {
 
    public static void isKthBitSet(int n,
                                   int k)
    {
        if ((n & (1 << (k - 1))) > 0)
            Console.Write("SET");
        else
            Console.Write("NOT SET");
    }
 
    // Driver code
    public static void Main()
    {
        int n = 5, k = 1;
 
        isKthBitSet(n, k);
    }
}
 
// This code is contributed by nitin mittal.

PHP




<?php
// PHP program to check if
// k-th bit of a given
// number is set or not
function isKthBitSet($n, $k)
{
    if ($n & (1 << ($k - 1)))
        echo "SET";
    else
        echo "NOT SET";
}
 
// Driver code
$n = 5; $k = 1;
isKthBitSet($n, $k);
 
// This code is contributed
// by akt_mit
?>

Javascript




<script>
    // Javascript program to check if k-th bit
    // of a given number is set or not.
     
    function isKthBitSet(n, k)
    {
        if ((n & (1 << (k - 1))) > 0)
            document.write("SET");
        else
            document.write("NOT SET");
    }
     
    let n = 5, k = 1;
   
      isKthBitSet(n, k);
                                 
</script>

Output:  



SET

 
Method 2 (Using Right Shift Operator) 
If we right shift n by k-1, we get the last bit as 1 if Kth bit is set else 0. 
 

C++




// CPP program to check if k-th bit
// of a given number is set or not using
// right shift operator.
#include <iostream>
using namespace std;
 
void isKthBitSet(int n, int k)
{
    if ((n >> (k - 1)) & 1)
        cout << "SET";
    else
        cout << "NOT SET";
}
 
// Driver code
int main()
{
    int n = 5, k = 1;
    isKthBitSet(n, k);
    return 0;
}

Java




// Java program to check if
// k-th bit of a given number
// is set or not using right
// shift operator.
import java.io.*;
 
class GFG
{
static void isKthBitSet(int n,
                        int k)
{
    if (((n >> (k - 1)) &
               1) > 0)
        System.out.println("SET");
    else
        System.out.println("NOT SET");
}
 
// Driver code
public static void main (String[] args)
{
    int n = 5, k = 1;
    isKthBitSet(n, k);
}
}
 
// This code is contributed
// by ajit

Python3




# PHP program to check if k-th bit of
# a given number is set or not using
# right shift operator.
 
def isKthBitSet(n, k):
    if ((n >> (k - 1)) and 1):
        print("SET")
    else:
        print("NOT SET")
 
# Driver code
n, k = 5, 1
isKthBitSet(n, k)
 
# This code contributed by
# PrinciRaj1992

C#




// C# program to check if
// k-th bit of a given number
// is set or not using right
// shift operator
using System;
 
class GFG
{
static void isKthBitSet(int n,
                        int k)
{
    if (((n >> (k - 1)) &
              1) > 0)
        Console.WriteLine("SET");
    else
        Console.WriteLine("NOT SET");
}
 
// Driver code
static public void Main ()
{
    int n = 5, k = 1;
    isKthBitSet(n, k);
}
}
 
// This code is contributed
// by ajit

PHP




<?php
// PHP program to check
// if k-th bit of a given
// number is set or not
// using right shift operator.
 
function isKthBitSet($n, $k)
{
    if (($n >> ($k - 1)) & 1)
        echo "SET";
    else
        echo "NOT SET";
}
 
// Driver code
$n = 5; $k = 1;
isKthBitSet($n, $k);
 
// This code is contributed
// by akt_mit
?>

Output: 
 

SET

 

This article is contributed by SAKSHI TIWARI. If you like GeeksforGeeks(We know you do!) 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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