Is Number Complement easy or hard?

Number Complement is classified as an Easy problem on LeetCode. The challenge mainly tests basic understanding of binary numbers, bit masks, and XOR operations rather than complex algorithms or data structures.

Number Complement Python/Java solution

In Python or Java, compute the mask using the bit length of the number: mask = (1 << num.bit_length()) - 1 in Python or (1 << (Integer.toBinaryString(num).length())) - 1 in Java. Return num ^ mask to flip all bits up to the most significant bit.

How to solve Number Complement in O(1)?

Compute the number of bits in num using a bit-length operation. Create a mask with (1 << bits) - 1 so all bits are set to 1 up to the most significant bit. The complement is then num ^ mask, which flips every bit in constant time.

What is the best approach for Number Complement?

The most common approach uses bit manipulation with a mask of all 1s covering the length of the number's binary representation. After building the mask, compute the complement using XOR: num ^ mask. This flips only the relevant bits and runs in O(log n) time with O(1) space.

Is Number Complement asked at Google/Amazon/Meta?

Number Complement is a classic bit manipulation problem commonly used in coding interviews to test understanding of binary representation and XOR operations. Variants of this problem appear in interview preparation sets for companies like Amazon and Google.

What data structure is used in Number Complement?

The solution does not require traditional data structures like arrays or hash maps. It relies purely on bit manipulation operations such as bit shifts, XOR, and mask creation to flip the bits of the integer.

What is the time complexity of Number Complement?

The typical mask-building approach runs in O(log n) time because it processes each bit of the number once. Space complexity is O(1) since only a few integer variables are used. If the language provides a direct bit-length function, the operation effectively becomes O(1).

Description Solution Video 7:58

476. Number Complement

Q: How to solve Number Complement in O(1)?

Compute the number of bits in num using a bit-length operation. Create a mask with (1 << bits) - 1 so all bits are set to 1 up to the most significant bit. The complement is then num ^ mask, which flips every bit in constant time.

Q: What is the best approach for Number Complement?

The most common approach uses bit manipulation with a mask of all 1s covering the length of the number's binary representation. After building the mask, compute the complement using XOR: num ^ mask. This flips only the relevant bits and runs in O(log n) time with O(1) space.

Q: Is Number Complement asked at Google/Amazon/Meta?

Number Complement is a classic bit manipulation problem commonly used in coding interviews to test understanding of binary representation and XOR operations. Variants of this problem appear in interview preparation sets for companies like Amazon and Google.

Q: What data structure is used in Number Complement?

The solution does not require traditional data structures like arrays or hash maps. It relies purely on bit manipulation operations such as bit shifts, XOR, and mask creation to flip the bits of the integer.

Q: What is the time complexity of Number Complement?

The typical mask-building approach runs in O(log n) time because it processes each bit of the number once. Space complexity is O(1) since only a few integer variables are used. If the language provides a direct bit-length function, the operation effectively becomes O(1).

Easy70.3% acceptance5 companies

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.

Given an integer num, return its complement.

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:

1 <= num < 2³¹

Note: This question is the same as 1009: https://leetcode.com/problems/complement-of-base-10-integer/

Asked at 5 companies

Cloudera JPMorgan Chase

Google Amazon Meta

Topics

Bit Manipulation

7:58

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1class Solution:
2    def findComplement(self, num: int) -> int:
3        

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