tech-interview-handbook/contents/algorithms/binary.md

id	title	toc_max_heading_level
binary	Binary	2

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
  • Practice with bit operations

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).
Multiple 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

Recommended questions

• Sum of Two Integers
• Number of 1 Bits
• Counting Bits
• Missing Number
• Reverse Bits
• Single Number

Recommended courses

import AlgorithmCourses from '../_courses/AlgorithmCourses.md'