CareerCup

Interviewer expected ans should be in O(1) as the best one.

Let num be the original number or the sequence of bits...
Do num2 = num - (num - 1)
difference = num2 - num
represent difference as power of 2... then the power gives the poisition of the bit sequence where first 1 appears if you start from that LSB end.

let num = 11111111111111100000000000000000000000000
a=num-1 = 11111111111111011111111111111111111111111
b=num^a = 00000000000000111111111111111111111111111
(b>>1)+1= 00000000000000100000000000000000000000000//answer

I understood the solution but I did not understand that how we can calculate the power of 2 because for calculating the power we will need to iterate the whole sequence which will result in O(n) not O(1).