How to turn on a particular bit in a number?

Given a number n and a value k, turn on the k’th bit in n.

Examples:

Input:  n = 4, k = 2
Output: 6

Input:  n = 3, k = 3
Output: 7

Input:  n = 64, k = 4
Output: 72

Input:  n = 64, k = 5
Output: 80

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

The idea is to use bitwise << and | operators. Using expression "(1 << (k – 1))“, we get a number which has all bits unset, except the k’th bit. If we do bitwise | of this expression with n, we get a number which has all bits same as n except the k’th bit which is 1.

Below is the implementation of above idea.

C++

 // CPP program to turn on a particular bit #include using namespace std;    // Returns a number that has all bits same as n // except the k'th bit which is made 1 int turnOnK(int n, int k) {     // k must be greater than 0     if (k <= 0)         return n;        // Do | of n with a number with all      // unset bits except the k'th bit     return (n | (1 << (k - 1))); }    // Driver program to test above function int main() {     int n = 4;     int k = 2;     cout << turnOnK(n, k);     return 0; }

Java

 // Java program to turn on a particular // bit class GFG {            // Returns a number that has all     // bits same as n except the k'th     // bit which is made 1     static int turnOnK(int n, int k)     {                    // k must be greater than 0         if (k <= 0)             return n;                // Do | of n with a number with         // all unset bits except the          // k'th bit         return (n | (1 << (k - 1)));     }            // Driver program to test above      // function     public static void main(String [] args)     {         int n = 4;         int k = 2;         System.out.print(turnOnK(n, k));     } }    // This code is contributed by Smitha

Python 3

 # Python 3 program to turn on a  # particular bit    # Returns a number that has all # bits same as n except the k'th # bit which is made 1 def turnOnK(n, k):        # k must be greater than 0     if (k <= 0):         return n        # Do | of n with a number     # with all unset bits except     # the k'th bit     return (n | (1 << (k - 1)))    # Driver program to test above  # function n = 4 k = 2 print(turnOnK(n, k))    # This code is contributed by # Smitha

C#

 // C# program to turn on a particular // bit using System;    class GFG {            // Returns a number that has all     // bits same as n except the k'th     // bit which is made 1     static int turnOnK(int n, int k)     {                    // k must be greater than 0         if (k <= 0)             return n;                // Do | of n with a number          // with all unset bits except          // the k'th bit         return (n | (1 << (k - 1)));     }            // Driver program to test above     // function     public static void Main()     {         int n = 4;         int k = 2;         Console.Write(turnOnK(n, k));     } }    // This code is contributed by Smitha

PHP



Output:

6

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