Binary cheatsheet for coding interviews

Introductionâ€‹

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.

Corner casesâ€‹

• Be aware and check for overflow/underflow
• Negative numbers

Techniquesâ€‹

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.

TechniqueCode
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 questionsâ€‹

These are essential questions to practice if you're studying for this topic.

These are recommended questions to practice after you have studied for the topic and have practiced the essential questions.

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