Binary cheatsheet for coding interviews
Introduction
Knowledge of binary number system and bit manipulation is less important in coding interviews as most Software Engineers do not have to deal with bits, which is more commonly used when dealing with lower level systems and programming languages. They are still asked sometimes, so you should at least still know how to convert a number from decimal form into binary form (and vice versa) in your chosen programming language.
Learning resources
- Readings
- Bits, Bytes, Building With Binary, basecs
- Bitwise operation, Wikipedia
- Videos
- Algorithms: Bit Manipulation, HackerRank
- Practice
Corner cases
- Be aware and check for overflow/underflow
- Negative numbers
Techniques
Questions involving binary representations and bitwise operations are asked sometimes and you must be absolutely familiar with how to convert a number from decimal form into binary form (and vice versa) in your chosen programming language.
Some helpful utility snippets:
| Technique | Code |
|---|---|
| Test kth bit is set | num & (1 << k) != 0 |
| Set kth bit | num |= (1 << k) |
| Turn off kth bit | num &= ~(1 << k) |
| Toggle the kth bit | num ^= (1 << k) |
| Multiply by 2k | num << k |
| Divide by 2k | num >> k |
| Check if a number is a power of 2 | (num & num - 1) == 0 or (num & (-num)) == num |
| Swapping two variables | num1 ^= num2; num2 ^= num1; num1 ^= num2 |
Essential questions
These are essential questions to practice if you're studying for this topic.
Recommended practice questions
These are recommended questions to practice after you have studied for the topic and have practiced the essential questions.
Source and license
This page is copied from the Tech Interview Handbook by Yangshun Tay (source commit e1d28e8), used under the MIT License — Copyright (c) 2017-Present Yangshun Tay. The license text is kept locally at /licenses/tech-interview-handbook.txt.