Leetcode 476  Number Complement
Problem Statement
Given a positive integer, output its complement number. The complement strategy is to flip the bits of its binary representation.
Note:
The given integer is guaranteed to fit within the range of a 32bit signed integer.
You could assume no leading zero bit in the integer’s binary representation.
Example 1:
Input: 5
Output: 2
Explanation: The binary representation of 5 is 101 (no leading zero bits), and its complement is 010. So you need to output 2.
Example 2:
Input: 1
Output: 0
Explanation: The binary representation of 1 is 1 (no leading zero bits), and its complement is 0. So you need to output 0.
Solution


Time: O(N) where N is the number of bits in num
Space: O(N) where N is the number of bits in num
Explanation
In python, to operate on the bitlevel there must be an O(log N)
call to bin()
which creates a binary string representation of num. Notice the usage of [2:] which strips out the leading ‘b’ character for binary string. After that, you’re just building up a binary string to represent each flipped bit and converting it to an integer by specifiying base 2.