Number Complement Python Solution with Tests

LeetCode 476, Easy. Topics: Bit Manipulation. View on LeetCode. Generate this problem as a practice environment: tested reference solution, 22 parametrized pytest cases, and a playground notebook:

lcpy gen -n 476   # by problem number
lcpy gen -s number_complement   # by problem name

Problem

The complement of an integer is the integer you get when you flip all the <code>0</code>‘s to <code>1</code>‘s and all the <code>1</code>‘s to <code>0</code>‘s in its binary representation. <ul> <li>For example, The integer <code>5</code> is <code>“101”</code> in binary and its complement is <code>“010”</code> which is the integer <code>2</code>.</li> </ul> Given an integer <code>num</code>, return its complement.

Examples

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.

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

1 <= num < 2^31

Solution

Reference implementation from solution.py on GitHub, full suite in test_solution.py:

class Solution:
    # Time: O(log num)
    # Space: O(1)
    def find_complement(self, num: int) -> int:
        mask = (1 << num.bit_length()) - 1
        return num ^ mask

Complexity

Time	Space
O(log num)	O(1)

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Number Complement Python Solution with Tests

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