Complement of Base 10 Integer — LeetCode 1009 Python Solution

The problem

The complement of an integer is the integer you get when you flip all the 0's to 1's and all the 1's to 0's in its binary representation. For example, The integer 5 is "101" in binary and its complement is "010" which is the integer 2.

Example

Input

n = 5

Output

2

Explanation

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

Python solution

class Solution:
    def bitwiseComplement(self, n: int) -> int:
        if n == 0:
            return 1
        ans = i = 0
        while n:
            ans |= ((n & 1 ^ 1) << i)
            i += 1
            n >>= 1
        return ans

Complexity

Pattern: Bit Manipulation

Use XOR, masks and the low-bit trick to replace whole data structures with an integer. LeetCode 1009. Complement of Base 10 Integer is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Bit Manipulation.

The bit manipulation guide has the Python template for the pattern and the 194 LeetCode problems that use it.

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