# LeetCode 476. Number Complement

## Description

https://leetcode.com/problems/number-complement/

Given a positive integer `num`, output its complement number. The complement strategy is to flip the bits of its binary representation.

Example 1:

```Input: num = 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: num = 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.
```

Constraints:

• The given integer `num` is guaranteed to fit within the range of a 32-bit signed integer.
• `num >= 1`
• You could assume no leading zero bit in the integerâ€™s binary representation.
• This question is the same as 1009: https://leetcode.com/problems/complement-of-base-10-integer/

## Explanation

Find the binary string and then convert it to complement number’s binary string. Finally convert back to 10 base integer.

## Python Solution

``````class Solution:
def findComplement(self, num: int) -> int:
binary = bin(num)[2:]

result = ""
for bit in binary:

if bit == "1":
result += "0"
else:
result += "1"

return int(result, 2)``````
• Time Complexity: O(N).
• Space Complexity: O(N).