Check whether K-th bit is set or not

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

Examples:

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

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

Check whether the K-th bit is set or not Using Left Shift Operator:

To solve the problem follow the below idea:

• 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)
• If bitwise AND of n and temp is non-zero, then result is SET else result is NOT SET.

Dry run of the above approach:

Input: 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.

Below is the implementation of the above approach:

C++

// CPP program to check if k-th bit
// of a given number is set or not
#include <bits/stdc++.h>
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;

    // Function call
    isKthBitSet(n, k);
    return 0;
}

C

// C program to check if k-th bit
// of a given number is set or not
#include <stdio.h>

void isKthBitSet(int n, int k)
{
    if (n & (1 << (k - 1)))
        printf("SET");
    else
        printf("NOT SET");
}

// Driver code
int main()
{
    int n = 5, k = 1;

    // Function call
    isKthBitSet(n, k);
    return 0;
}

// this code is contributed by devendrasaluke

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;

        // Function call
        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
if __name__ == "__main__":
    n = 5
    k = 1

    # Function call
    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;

        // Function call
        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;

// Function call
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

Time Complexity: O(1)
Auxiliary Space: O(1)

Check whether the K-th bit is set or not Using Right Shift Operator:

To solve the problem follow the below idea:

If we right shift n by k-1, we get the last bit as 1 if the Kth bit is set else 0

Below is the implementation of the above approach:

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;

    // Function call
    isKthBitSet(n, k);
    return 0;
}

C

// C program to check if k-th bit
// of a given number is set or not using
// right shift operator.
#include <stdio.h>

void isKthBitSet(int n, int k)
{
    if ((n >> (k - 1)) & 1)
        printf("SET");
    else
        printf("NOT SET");
}

// Driver code
int main()
{
    int n = 5, k = 1;

    // Function call
    isKthBitSet(n, k);
    return 0;
}
// this code is contributed by devendrasolunke

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;

        // Function call
        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
if __name__ == "__main__":
    n, k = 5, 1

    # Function call
    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;

        // Function call
        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;

// Function call
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 using right
// shift operator.

function isKthBitSet(n, k)
{
    if (((n >> (k - 1)) &
               1) > 0)
        document.write("SET");
    else
        document.write("NOT SET");
}

// Driver Code

    let n = 5, k = 1;
    isKthBitSet(n, k);

// This code is contributed by sanjoy_62.
</script>

Output

SET

Time Complexity: O(1)
Auxiliary Space: O(1)

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