LeetCode 1009. Complement of Base 10 Integer

Description

https://leetcode.com/problems/complement-of-base-10-integer/

Every non-negative integer N has a binary representation.  For example, 5 can be represented as "101" in binary, 11 as "1011" in binary, and so on.  Note that except for N = 0, there are no leading zeroes in any binary representation.

The complement of a binary representation is the number in binary you get when changing every 1 to a 0 and 0 to a 1.  For example, the complement of "101" in binary is "010" in binary.

For a given number N in base-10, return the complement of it’s binary representation as a base-10 integer.

Example 1:

Input: 5
Output: 2
Explanation: 5 is "101" in binary, with complement "010" in binary, which is 2 in base-10.

Example 2:

Input: 7
Output: 0
Explanation: 7 is "111" in binary, with complement "000" in binary, which is 0 in base-10.

Example 3:

Input: 10
Output: 5
Explanation: 10 is "1010" in binary, with complement "0101" in binary, which is 5 in base-10.

Note:

1. 0 <= N < 10^9
2. This question is the same as 476: https://leetcode.com/problems/number-complement/

Explanation

Find complement’s binary string and then convert it back to integer.

Python Solution

class Solution:
    def bitwiseComplement(self, N: int) -> int:
        
        binary_n = bin(N)

        result = ""
        for c in binary_n[2:]:
            if c == '0':
                result += '1'
            else:
                result += '0'
                
        
        return int(result, 2)