Get the position of rightmost unset bit

Given a non-negative number n. Find the position of rightmost unset bit in the binary representation of n, considering the last bit at position 1, 2nd last bit at position 2 and so on. If no 0's are there in the binary representation of n. then print "-1".
Examples: 
 

Input : n = 9
Output : 2
(9)10 = (1001)2
The position of rightmost unset bit in the binary
representation of 9 is 2.

Input : n = 32
Output : 1

 

Approach: Following are the steps:
 

1. If n = 0, return 1.
2. If all bits of n are set, return -1. Refer this post.
3. Else perform bitwise not on the given number(operation equivalent to 1’s complement). Let it be num = ~n.
4. Get the position of rightmost set bit of num. This will be the position of rightmost unset bit of n.

 

Output: 
 

2

Time Complexity - O(1)

Space Complexity - O(1)