How to turn off a particular bit in a number?

Given a number n and a value k, turn off the kth bit in n. Please note that k = 1 means the rightmost bit.

Examples: 

Input: n = 15, k = 1
Output: 14

Input: n = 14, k = 1
Output: 14
The rightmost bit was already off, so no change.

Input: n = 15, k = 2
Output: 13

Input: n = 15, k = 3
Output: 11

Input: n = 15, k = 4
Output: 7

Input: n = 15, k >= 5
Output: 15 

The idea is to use bitwise <<, & and ~ operators. Using the expression "~(1 << (k - 1))", we get a number that has all bits set, except the kth bit. If we do bitwise & of this expression with n, we get a number that has all bits the same as n except the kth bit which is 0. 

Below is the implementation of the above idea. 

7

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

Method 2: Using XOR operator.

Left shift 1 by (k - 1) times and check if kth bit is set or not, if set then take XOR for togging the kth bit.

Below is the implementation of the above approach:

7

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

Exercise: Write a function turnOnK() that turns the k'th bit on.