Leetcode #1009: Complement of Base 10 Integer
In this guide, we solve Leetcode #1009 Complement of Base 10 Integer in Python and focus on the core idea that makes the solution efficient.
You will see the intuition, the step-by-step method, and a clean Python implementation you can use in interviews.
Problem Statement
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.
Quick Facts
- Difficulty: Easy
- Premium: No
- Tags: Bit Manipulation
Intuition
The problem structure lets us track state with bitwise operations.
Bit operations are constant time and avoid extra memory.
Approach
Apply XOR/AND/OR and shifts to maintain the required invariant.
Aggregate the result in a single pass.
Steps:
- Identify a bitwise invariant.
- Combine values with bit operations.
- Return the aggregated result.
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
The time complexity is , where is the given decimal number. The space complexity is .
Edge Cases and Pitfalls
Watch for boundary values, empty inputs, and duplicate values where applicable. If the problem involves ordering or constraints, confirm the invariant is preserved at every step.
Summary
This Python solution focuses on the essential structure of the problem and keeps the implementation interview-friendly while meeting the constraints.