Java Challenges : 100+ Proven Tasks That Will Prepare You for Anything

Expand your knowledge of Java with this entertaining learning guide, which features 100+ exercises and programming challenges. Java Challenges will prepare you for your next exam or job interview, and covers many practical topics, such as strings, arrays, data structures, recursion, and date and time. The APIs and other material included in this book are Java 17 compatible. Each topic is addressed in its own separate chapter, starting with an introduction to the basics and followed by multiple exercises of varying degrees of difficulty, helping you to improve your programming skills effectively. Detailed sample solutions, including the algorithms used for all tasks, are included to maximize your understanding of each area. Author Michael Inden also describes alternative solutions and analyzes possible pitfalls and typical errors. Three appendices round out the book: one covering JShell, which is often helpful for trying out the code snippets and examples in the book, followed by an introduction to JUnit 5 for unit testing and verifying solutions, while the final appendix explains O-notation for estimating performance. After reading this book, you'll be prepared to take the next step in your career or tackle your next personal project. All source code is freely available for download via the Apress website. What You Will Learn Improve your Java knowledge by solving enjoyable but challenging programming puzzles Solve mathematical problems, recursions, strings, arrays and more Manage data processing and data structures like lists, sets, maps Handle advanced recursion as well as binary trees, sorting and searching Gamify key fundamentals for fun and easier reinforcement Who This Book Is For Professional software developers, makers, as well as computer science teachers and students. At least some prior experience with Java programming is recommended. Table of Contents About the Author About the Technical Reviewer Preface Practice Makes Perfect Why This Book? Who Is This Book Aimed At? What Does This Book Teach? Practical Tips and Advice Difficulty Level at a Glance Structure of This Book Conventions and Executable Programs Character Sets Used Abbreviations Used Java Version(s) Used Classes Used from the JDK Downloads, Source Code, and Executables Acknowledgements (English Book) Acknowledgements (German Book) Suggestions and Criticism Chapter 1: Introduction 1.1 Structure of the Chapters 1.1.1 Introduction 1.1.2 Exercises 1.1.3 Solutions 1.2 Basic Structure of the Eclipse Project 1.3 Basic Framework for Unit Tests 1.4 Note on Programming Style 1.4.1 Thoughts on Source Code Compactness 1.4.2 Example 1 1.4.3 Example 2 1.4.4 Thoughts on final and var 1.4.5 Notes on Method Visibility 1.4.6 Block Comments in Listings 1.4.7 Thoughts on Formatting 1.5 Trying Out the Examples and Solutions 1.6 Let’s Go: Discovering Java Challenge Part I: Fundamentals Chapter 2: Mathematical Problems 2.1 Introduction 2.1.1 Short Introduction to Division and Modulo 2.1.2 Short Introduction to Divider 2.1.3 Short Introduction to Prime Numbers 2.1.4 Roman Numbers 2.1.5 Rules 2.1.6 Examples 2.1.7 Noteworthy 2.1.8 Number Games 2.1.9 Perfect Numbers 2.1.10 Armstrong Numbers 2.1.11 Algorithm for a Simple Checksum 2.2 Exercises 2.2.1 Exercise 1: Basic Arithmetic (★✩✩✩✩) Exercise 1a: Basic Arithmetic Operations (★✩✩✩✩) Examples Exercise 1b: Statistics (★★✩✩✩) Examples Exercise 1c: Even or Odd Number (★✩✩✩✩) 2.2.2 Exercise 2: Number as Text (★★✩✩✩) Examples 2.2.3 Exercise 3: Perfect Numbers (★★✩✩✩) Examples 2.2.4 Exercise 4: Prime Numbers (★★✩✩✩) Examples 2.2.5 Exercise 5: Prime Number Pairs (★★✩✩✩) Examples 2.2.6 Exercise 6: Checksum (★★✩✩✩) Examples 2.2.7 Exercise 7: Roman Numbers (★★★★✩) Exercise 7a: Roman Numbers → Decimal Numbers (★★★✩✩) Exercise 7b: Decimal Numbers → Roman Numbers (★★★★✩) Examples 2.2.8 Exercise 8: Combinatorics (★★✩✩✩) Exercise 8a: Computation of a2 + b2 = c2 Exercise 8b: Computation of a 2 + b 2 = c 2 + d 2 2.2.9 Exercise 9: Armstrong Numbers (★★✩✩✩) Examples 2.2.10 Exercise 10: Max Change Calculator (★★★★✩) Examples 2.2.11 Exercise 11: Related Numbers (★★✩✩✩) Examples 2.2.12 Exercise 12: Prime Factorization (★★★✩✩) Examples 2.3 Solutions 2.3.1 Solution 1: Basic Arithmetic (★✩✩✩✩) Solution 1a: Basic Arithmetic Operations (★✩✩✩✩) Examples Solution 1b: Statistics (★★✩✩✩) Examples Solution 1c: Even or Odd Number (★✩✩✩✩) Verification 2.3.2 Solution 2: Number as Text (★★✩✩✩) Examples Verification 2.3.3 Solution 3: Perfect Numbers (★★✩✩✩) Examples Verification Implementation Optimization 2.3.4 Solution 4: Prime Numbers (★★✩✩✩) Examples Verification 2.3.5 Solution 5: Prime Number Pairs (★★✩✩✩) Examples Optimization of the Implementation Verification 2.3.6 Solution 6: Checksum (★★✩✩✩) Examples 2.3.7 Solution 7: Roman Numbers (★★★★✩) Solution 7a: Roman Numbers → Decimal Numbers (★★★✩✩) Examples Solution 7b: Decimal Numbers → Roman Numbers (★★★★✩) Verification 2.3.8 Solution 8: Combinatorics (★★✩✩✩) Solution 8a: Computation of a2 + b2 = c2 Bonus: Reduce the Running Time of O(n3) to O(n2) (★★★✩✩) Verification Solution 8b: Computation of a2 + b2 = c2 + d2 Bonus: Reduce the Running Time of O(n4) to O(n3) (★★★✩✩) Verification 2.3.9 Solution 9: Armstrong Numbers (★★✩✩✩) Examples Verification Bonus (★★★✩✩) Verification 2.3.10 Solution 10: Max Change Calculator (★★★★✩) Examples Verification 2.3.11 Solution 11: Related Numbers (★★✩✩✩) Examples Verification 2.3.12 Solution 12: Prime Factorization (★★★✩✩) Examples Verification Chapter 3: Recursion 3.1 Introduction 3.1.1 Mathematical Examples Example 1: Factorial Example 2: Calculation of the Sum of Numbers Up to n Example 3: Fibonacci Numbers 3.1.2 Algorithmic Examples Example 1: Palindrome – Recursive Variant Example 1: Palindrome – Iterative Variant Example 2: Fractal as an Example 3.1.3 Steps When Multiplying the Digits of a Number 3.1.4 Typical Problems Endless Calls and StackOverflowError Unexpected Parameter Values 3.2 Exercises 3.2.1 Exercise 1: Fibonacci (★★✩✩✩) Exercise 1a: Fibonacci Recursive (★✩✩✩✩) Exercise 1b: Fibonacci Iterative (★★✩✩✩) 3.2.2 Exercise 2: Process Digits (★★✩✩✩) Exercise 2a: Count Digits (★★✩✩✩) Examples Exercise 2b: Cross Sum (★★✩✩✩) 3.2.3 Exercise 3: GCD (★★✩✩✩) Exercise 3a: GCD Recursive (★✩✩✩✩) Examples Exercise 3b: GCD Iterative (★★✩✩✩) Exercise 3c: LCM (★✩✩✩✩) Examples 3.2.4 Exercise 4: Reverse String (★★✩✩✩) Examples 3.2.5 Exercise 5: Array Sum (★★✩✩✩) Examples 3.2.6 Exercise 6: Array Min (★★✩✩✩) Examples 3.2.7 Exercise 7: Conversions (★★✩✩✩) Exercise 7a: Binary (★★✩✩✩) Examples Exercise 7b: Octal and Hexadecimal Numbers (★★✩✩✩) Examples 3.2.8 Exercise 8: Exponential Function (★★✩✩✩) Exercise 8a: Power of Two (★★✩✩✩) Examples Exercise 8b: Exponentiation Recursive (★★✩✩✩) Exercise 8c: Exponentiation Iterative (★★✩✩✩) Examples 3.2.9 Exercise 9: Pascal’s Triangle (★★✩✩✩) 3.2.10 Exercise 10: Number Palindromes (★★★★✩) Examples 3.2.11 Exercise 11: Permutations (★★★✩✩) Examples 3.2.12 Exercise 12: Count Substrings (★★✩✩✩) Examples 3.2.13 Exercise 13: Ruler (★★✩✩✩) 3.3 Solutions 3.3.1 Solution 1: Fibonacci (★★✩✩✩) Solution 1a: Fibonacci Recursive (★✩✩✩✩) Solution 1b: Fibonacci Iterative (★★✩✩✩) Verification 3.3.2 Solution 2: Process Digits (★★✩✩✩) Solution 2a: Count Digits (★★✩✩✩) Examples Solution 2b: Cross Sum (★★✩✩✩) Verification 3.3.3 Solution 3: GCD (★★✩✩✩) Solution 3a: GCD Recursive (★✩✩✩✩) Examples Solution 3b: GCD Iterative (★★✩✩✩) Verification Solution 3c: LCM (★✩✩✩✩) Examples Verification 3.3.4 Solution 4: Reverse String (★★✩✩✩) Examples Verification 3.3.5 Solution 5: Array Sum (★★✩✩✩) Examples Verification 3.3.6 Solution 6: Array Min (★★✩✩✩) Examples Verification 3.3.7 Solution 7: Conversions (★★✩✩✩) Solution 7a: Binary (★★✩✩✩) Examples Solution 7b: Octal and Hexadecimal Numbers (★★✩✩✩) Examples Verification 3.3.8 Solution 8: Exponential Function (★★✩✩✩) Solution 8a: Power of Two (★★✩✩✩) Examples Solution 8b: Exponentiation Recursive (★★✩✩✩) Solution 8c: Exponentiation Iterative (★★✩✩✩) Examples Verification 3.3.9 Solution 9: Pascal’s Triangle (★★✩✩✩) Verification 3.3.10 Solution 10: Number Palindromes (★★★★✩) Examples Verification 3.3.11 Solution 11: Permutations (★★★✩✩) Examples Verification 3.3.12 Solution 12: Count Substrings (★★✩✩✩) Examples Verification 3.3.13 Solution 13: Ruler (★★✩✩✩) Verification Chapter 4: Strings 4.1 Introduction 4.1.1 The Interface CharSequence 4.1.2 The Class String Methods Relevant to Practice 4.1.3 The Classes StringBuffer and StringBuilder Additional Functionality and Comparison with the Class String 4.1.4 The Class Character Example 4.1.5 Examples Related to Character and String Homemade Conversions with Character Example: String Processing 4.2 Exercises 4.2.1 Exercise 1: Number Conversions (★★✩✩✩) Examples Exercise 1a (★✩✩✩✩) Exercise 1b (★★✩✩✩) Exercise 1c (★★✩✩✩) 4.2.2 Exercise 2: Joiner (★✩✩✩✩) Exercise 2a (★✩✩✩✩) Exercise 2b (★✩✩✩✩) Examples 4.2.3 Exercise 3: Reverse String (★★✩✩✩) Examples 4.2.4 Exercise 4: Palindrome (★★★✩✩) Exercise 4a (★★✩✩✩) Examples Exercise 4b (★★★✩✩) 4.2.5 Exercise 5: No Duplicate Chars (★★★✩✩) Examples 4.2.6 Exercise 6: Remove Duplicate Letters (★★★✩✩) Examples 4.2.7 Exercise 7: Capitalize (★★✩✩✩) Exercise 7a (★★✩✩✩) Examples Exercise 7b: Modification (★★✩✩✩) Exercise 7c: Special Treatment (★★✩✩✩) Example 4.2.8 Exercise 8: Rotation (★★✩✩✩) Examples 4.2.9 Exercise 9: Well-Formed Braces (★★✩✩✩) Examples 4.2.10 Exercise 10: Anagram (★★✩✩✩) Examples 4.2.11 Exercise 11: Morse Code (★★✩✩✩) Examples 4.2.12 Exercise 12: Pattern Checker (★★★✩✩) Examples 4.2.13 Exercise 13: Tennis Score (★★★✩✩) Examples 4.2.14 Exercise 14: Version Numbers (★★✩✩✩) Examples 4.2.15 Exercise 15: Conversion strToLong (★★✩✩✩) Examples 4.2.16 Exercise 16: Print Tower (★★★✩✩) 4.3 Solutions 4.3.1 Solution 1: Number Conversions (★★✩✩✩) Examples Solution 1a (★✩✩✩✩) Solution 1b (★★✩✩✩) Solution 1c (★★✩✩✩) Verification 4.3.2 Solution 2: Joiner (★✩✩✩✩) Solution 2a (★✩✩✩✩) Examples Solution 2b (★✩✩✩✩) Verification 4.3.3 Solution 3: Reverse String (★★✩✩✩) Examples Verification 4.3.4 Solution 4: Palindrome (★★★✩✩) Solution 4a (★★✩✩✩) Examples Solution 4b (★★★✩✩) Verification 4.3.5 Solution 5: No Duplicate Chars (★★★✩✩) Examples Verification 4.3.6 Solution 6: Remove Duplicate Letters (★★★✩✩) Examples Verification 4.3.7 Solution 7: Capitalize (★★✩✩✩) Solution 7a (★★✩✩✩) Examples Solution 7b: Modification (★★✩✩✩) Solution 7c: Special Treatment (★★✩✩✩) Example Verification 4.3.8 Solution 8: Rotation (★★✩✩✩) Examples Verification 4.3.9 Solution 9: Well-Formed Braces (★★✩✩✩) Examples Verification 4.3.10 Solution 10: Anagram (★★✩✩✩) Examples Verification 4.3.11 Solution 11: Morse Code (★★✩✩✩) Examples Bonus Verification 4.3.12 Solution 12: Pattern Checker (★★★✩✩) Examples Verification 4.3.13 Solution 13: Tennis Score (★★★✩✩) Examples Verification 4.3.14 Solution 14: Version Numbers (★★✩✩✩) Examples Verification Bonus 4.3.15 Solution 15: Conversion strToLong (★★✩✩✩) Examples Verification Bonus: Enable the Parsing of Octal Numbers Verification 4.3.16 Solution 16: Print Tower (★★★✩✩) Verification Chapter 5: Arrays 5.1 Introduction 5.1.1 One-Dimensional Arrays Textual Output Example 1: Swapping Elements Example 2: Basic Functionality for Arrays Example 3: Remove Duplicates Example 4: Rotation by One or More Positions 5.1.2 Multidimensional Arrays Introductory Example Modeling Directions 5.1.3 Typical Errors 5.2 Exercises 5.2.1 Exercise 1: Even Before Odd Numbers (★★✩✩✩) Examples 5.2.2 Exercise 2: Flip (★★✩✩✩) Examples 5.2.3 Exercise 3: Palindrome (★★✩✩✩) Examples 5.2.4 Exercise 4: Inplace Rotate (★★★✩✩) Exercise 4a: Iterative (★★★✩✩) Example Exercise 4b: Recursive (★★★✩✩) 5.2.5 Exercise 5: Jewels Board Init (★★★✩✩) Exercise 5a: Initialize (★★★✩✩) Example Exercise 5b: Validity Check (★★★✩✩) Example 5.2.6 Exercise 6: Jewels Board Erase Diamonds (★★★★✩) Exercise 6a: Erase (★★★★✩) Examples Exercise 6b: Falling Down (★★★✩✩) Example 5.2.7 Exercise 7: Spiral Traversal (★★★★✩) Example 5.2.8 Exercise 8: Add One to Array as Number (★★✩✩✩) Examples 5.2.9 Exercise 9: Sudoku Checker (★★★✩✩) Example Example 5.2.10 Exercise 10: Flood Fill (★★✩✩✩) Exercise 10a (★★✩✩✩) Example Exercise 10b (★★✩✩✩) Example 5.2.11 Exercise 11: Array Merge (★★✩✩✩) Examples 5.2.12 Exercise 12: Array Min and Max (★★✩✩✩) Exercise 12a: Min and Max (★✩✩✩✩) Example Exercise 12b: Min and Max Pos (★★✩✩✩) Examples 5.2.13 Exercise 13: Array Split (★★★✩✩) Examples Exercise 13a: Array Split (★★✩✩✩) Exercise 13b: Array Split Inplace (★★★✩✩) Exercise 13c: Array Split Quick Sort Partition (★★★✩✩) Examples 5.2.14 Exercise 14: Minesweeper Board (★★★✩✩) Exercise 14a (★★✩✩✩) Example Exercise 14b (★★★✩✩) Examples Exercise 14c (★★✩✩✩) Example 5.3 Solutions 5.3.1 Solution 1: Even Before Odd Numbers (★★✩✩✩) Examples Optimized Algorithm: Improved Running Time Optimized Algorithm: Less Copying Verification 5.3.2 Solution 2: Flip (★★✩✩✩) Examples Verification 5.3.3 Solution 3: Palindrome (★★✩✩✩) Examples Verification 5.3.4 Solution 4: Inplace Rotate (★★★✩✩) Solution 4a: Iterative (★★★✩✩) Example Solution 4b: Recursive (★★★✩✩) Verification 5.3.5 Solution 5: Jewels Board Init (★★★✩✩) Solution 5a: Initialize (★★★✩✩) Example Solution to the Bonus Task: Diagonal Check (★★★✩✩) Verification Solution 5b: Validity Check (★★★✩✩) Example Verification 5.3.6 Solution 6: Jewels Board Erase Diamonds (★★★★✩) Solution 6a: Erase (★★★★✩) Examples Verification Solution 6b: Falling Down (★★★✩✩) Example Verification Overall Verification 5.3.7 Solution 7: Spiral Traversal (★★★★✩) Example Verification 5.3.8 Solution 8: Add One to Array as Number (★★✩✩✩) Examples Verification 5.3.9 Solution 9: Sudoku Checker (★★★✩✩) Example Verification Bonus Example Verification 5.3.10 Solution 10: Flood Fill (★★✩✩✩) Solution 10a (★★✩✩✩) Example Verification Solution 10b (★★✩✩✩) Example Verification 5.3.11 Solution 11: Array Merge (★★✩✩✩) Examples Verification 5.3.12 Solution 12: Array Min and Max (★★✩✩✩) Solution 12a: Min and Max (★✩✩✩✩) Examples Solution 12b: Min and Max Pos (★★✩✩✩) Examples Verification 5.3.13 Solution 13: Array Split (★★★✩✩) Examples Solution 13a: Array Split (★★✩✩✩) Solution 13b: Array Split Inplace (★★★✩✩) Solution 13c: Array Split Quick Sort Partition (★★★✩✩) Examples Verification 5.3.14 Solution 14: Minesweeper Board (★★★✩✩) Solution 14a (★★✩✩✩) Example Verification Solution 14b (★★★✩✩) Examples Verification Solution 14c (★★✩✩✩) Example Verification Chapter 6: Date Processing 6.1 Introduction 6.1.1 The Enumerations DayOfWeek and Month 6.1.2 The Classes LocalDate, LocalTime, and LocalDateTime Extensions in the LocalDate Class with Java 9 6.1.3 The Class ZonedDateTime 6.1.4 The class ZoneId 6.1.5 The Class Duration 6.1.6 The Class Period 6.1.7 Date Arithmetic Predefined TemporalAdjusters More Specific Predefined TemporalAdjusters Example Example: Define TemporalAdjuster Yourself 6.1.8 Formatting and Parsing 6.2 Exercises 6.2.1 Exercise 1: Leap Years (★✩✩✩✩) Examples 6.2.2 Exercise 2: Basic Knowledge Date-API (★★✩✩✩) Exercise 2a: Creation (★✩✩✩✩) Exercise 2b: Time Durations (★★✩✩✩) 6.2.3 Exercise 3: Length of Month (★★✩✩✩) Exercise 3a: Calculations (★✩✩✩✩) Exercise 3b: Length of Month (★★✩✩✩) 6.2.4 Exercise 4: Time Zones (★★✩✩✩) Example 6.2.5 Exercise 5: Time Zone Calculation (★★✩✩✩) Example 6.2.6 Exercise 6: Calculations with LocalDate Exercise 6a: Friday the 13th (★★✩✩✩) Example Exercise 6b: Several Occurrences of Friday the 13th (★★✩✩✩) Examples 6.2.7 Exercise 7: Calendar Output (★★★✩✩) Example 6.2.8 Exercise 8: Weekdays (★✩✩✩✩) Exercise 8a: Weekdays (★✩✩✩✩) Examples Exercise 8b: Date (★✩✩✩✩) Example Exercise 8c: Day in Month or Year (★✩✩✩✩) Examples 6.2.9 Exercise 9: Sundays and Leap Years (★★✩✩✩) Exercise 9a: Sundays Examples Exercise 9b: Leap Years Examples 6.2.10 Exercise 10: TemporalAdjuster (★★★✩✩) Examples 6.2.11 Exercise 11: NthWeekdayAdjuster (★★★✩✩) Examples 6.2.12 Exercise 12: Payday TemporalAdjuster (★★★✩✩) Example 6.2.13 Exercise 13: Formatting and Parsing (★★✩✩✩) Examples 6.2.14 Exercise 14: Fault-Tolerant Parsing (★★✩✩✩) Examples 6.3 Solutions 6.3.1 Solution 1: Leap Years (★✩✩✩✩) Examples Verification 6.3.2 Solution 2: Basic Knowledge Date-API (★★✩✩✩) Solution 2a: Creation (★✩✩✩✩) Solution 2b: Time Durations (★★✩✩✩) 6.3.3 Solution 3: Length of Month (★★✩✩✩) Solution 3a: Calcu lations (★✩✩✩✩) Solution 3b: Length of Month (★★✩✩✩) Verification 6.3.4 Solution 4: Time Zones (★★✩✩✩) Example Verification 6.3.5 Solution 5: Time Zone Calculation (★★✩✩✩) Example Verification 6.3.6 Solution 6: Calculations With LocalDate Exercise 6a: Friday the 13th (★★✩✩✩) Example Solution 6b: Several Occurrences of Friday the 13th (★★✩✩✩) Examples Verification 6.3.7 Solution 7: Calendar Output (★★★✩✩) Example Verification 6.3.8 Solution 8: Weekdays (★✩✩✩✩) Solution 8a: Weekdays (★✩✩✩✩) Examples Verification Solution 8b: Date (★✩✩✩✩) Example Verification Solution 8c: Day in Month or Year (★✩✩✩✩) Examples Verification 6.3.9 Solution 9: Sundays and Leap Years (★★✩✩✩) Solution 9a: Sundays Examples Verification Solution 9b: Leap Years Examples Verification 6.3.10 Solution 10: TemporalAdjuster (★★★✩✩) Examples Verification 6.3.11 Solution 11: NthWeekdayAdjuster (★★★✩✩) Examples Verification 6.3.12 Solution 12: Payday TemporalAdjuster (★★★✩✩) Example Verification 6.3.13 Solution 13: Formatting and Parsing (★★✩✩✩) Examples Verification 6.3.14 Solution 14: Fault-Tolerant Parsing (★★✩✩✩) Examples Verification Chapter 7: Basic Data Structures: Lists, Sets, and Maps 7.1 Introduction 7.1.1 The Interface Collection 7.1.2 Lists and the Interface List The Interface List 7.1.3 Sets and the Interface Set The Interface Set 7.1.4 Key-Value Mappings and the Interface Map The Interface Map 7.1.5 The Stack as a LIFO Data Structure Example 7.1.6 The Queue as a FIFO Data Structure Example 7.2 Exercises 7.2.1 Exercise 1: Set Operations (★★✩✩✩) Exercise 1a: Common Elements (★★✩✩✩) Examples Exercise 1b: Set Operations (★★✩✩✩) Examples 7.2.2 Exercise 2: List Reverse (★★✩✩✩) Exercise 2a: List Reverse (★★✩✩✩) Examples Exercise 2b: List Reverse Inplace (★★✩✩✩) Exercise 2c: List Reverse Without Performant Index Access (★★✩✩✩) 7.2.3 Exercise 3: Remove Duplicates (★★✩✩✩) Examples 7.2.4 Exercise 4: Maximum Profit (★★★✩✩) Examples 7.2.5 Exercise 5: Longest Sequence (★★★✩✩) Examples 7.2.6 Exercise 6: Own Stack (★★✩✩✩) 7.2.7 Exercise 7: Well-Formed Braces (★★✩✩✩) Examples 7.2.8 Exercise 8: Check a Magic Triangle (★★★✩✩) Examples 7.2.9 Exercise 9: Pascal’s Triangle (★★★✩✩) Example 7.2.10 Exercise 10: Most Frequent Elements (★★✩✩✩) Examples 7.2.11 Exercise 11: Addition of Digits (★★★✩✩) Exercise 11a: Addition (★★★✩✩) Examples Exercise 11b: Addition Inverse (★★★✩✩) Examples 7.2.12 Exercise 12: Compound Key (★★✩✩✩) Examples 7.2.13 Exercise 13: List Merge (★★✩✩✩) Examples 7.2.14 Exercise 14: Excel Magic Select (★★✩✩✩) Examples 7.3 Solutions 7.3.1 Solution 1: Set Operations (★★✩✩✩) Solution 1a: Common Elements (★★✩✩✩) Examples Verification Solution 1b: Set Operations (★★✩✩✩) Examples Verification 7.3.2 Solution 2: List Reverse (★★✩✩✩) Solution 2a: List Reverse (★★✩✩✩) Examples Solution 2b: List Reverse Inplace (★★✩✩✩) Solution 2c: List Reverse Without Performant Index Access (★★✩✩✩) Verification 7.3.3 Solution 3: Remove Duplicates (★★✩✩✩) Examples Verification 7.3.4 Solution 4: Maximum Profit (★★★✩✩) Examples Verification 7.3.5 Solution 5: Longest Sequence (★★★✩✩) Examples Verification 7.3.6 Solution 6: Own Stack (★★✩✩✩) Verification 7.3.7 Solution 7: Well-Formed Braces (★★✩✩✩) Examples Verification Bonus 7.3.8 Solution 8: Check a Magic Triangle (★★★✩✩) Examples Verification Verification 7.3.9 Solution 9: Pascal’s Triangle (★★★✩✩) Example Verification 7.3.10 Solution 10: Most Frequent Elements (★★✩✩✩) Examples Verification 7.3.11 Solution 11: Addition of Digits (★★★✩✩) Solution 11a: Addition (★★★✩✩) Examples Verification Solution 11b: Addition Inverse (★★★✩✩) Examples Verification 7.3.12 Solution 12: Compound Key (★★✩✩✩) Examples Verification 7.3.13 Solution 13: List Merge (★★✩✩✩) Examples Verification 7.3.14 Solution 14: Excel Magic Select (★★✩✩✩) Examples Verification Part II: More Advanced and Tricky Topics Chapter 8: Recursion Advanced 8.1 Memoization 8.1.1 Memoization for Fibonacci Numbers 8.1.2 Memoization for Pascal’s Triangle Conclusion 8.2 Backtracking 8.2.1 n-Queens Problem Algorithm What Is Still Missing in the Implementation? What is the Next Step? 8.3 Exercises 8.3.1 Exercise 1: Towers of Hanoi (★★★✩✩) Example 8.3.2 Exercise 2: Edit Distance (★★★★✩) Examples 8.3.3 Exercise 3: Longest Common Subsequence (★★★✩✩) Examples 8.3.4 Exercise 4: Way Out of a Labyrinth (★★★✩✩) Example 8.3.5 Exercise 5: Sudoku Solver (★★★★✩) Example 8.3.6 Exercise 6: Math Operator Checker (★★★★✩) Examples 8.3.7 Exercise 7: Water Jug Problem (★★★✩✩) Examples 8.3.8 Exercise 8: All Palindrome Substrings (★★★★✩) Examples 8.3.9 Exercise 9: n-Queens Problem (★★★✩✩) Example 8.4 Solutions 8.4.1 Solution 1: Towers of Hanoi (★★★✩✩) Example Bonus: Create a Console-Based Graphical Format Verification 8.4.2 Solution 2: Edit Distance (★★★★✩) Examples Verification Verification Bonus: Optimize Edit Distance with Memoization (★★★✩✩) 8.4.3 Solution 3: Longest Common Subsequence (★★★✩✩) Examples Verification Bonus: Use Memoization for Longest Common Subsequence 8.4.4 Solution 4: Way Out of a Labyrinth (★★★✩✩) Example Verification Alternative 8.4.5 Solution 5: Sudoku Solver (★★★★✩) Example Verification Reasonable Optimizations 8.4.6 Solution 6: Math Operator Checker (★★★★✩) Examples Variant with Streams Variant as of Java 15 Verification 8.4.7 Solution 7: Water Jug Problem (★★★✩✩) Examples Verification 8.4.8 Solution 8: All Palindrome Substrings (★★★★✩) Examples Bonus: Find the Longest of All Palindrome Substrings Verification 8.4.9 Solution 9: n-Queens Problem (★★★✩✩) Example Verification Alternative Solution Approach Verification Chapter 9: Binary Trees 9.1 Introduction 9.1.1 Structure, Terminology, and Examples of Use 9.1.2 Binary Trees 9.1.3 Binary Trees with Order: Binary Search Trees 9.1.4 Traversals Breadth-First/Level-Order Depth-First Searches 9.1.5 Balanced Trees and Other Properties The Properties Level and Height The Properties Completeness and Perfectness 9.1.6 Trees for the Examples and Exercises Tree with Letters and Numbers Trees with Textual and Real Digits 9.2 Exercises 9.2.1 Exercise 1: Tree Traversal (★★✩✩✩) 9.2.2 Exercise 2: Preorder, Inorder, and Postorder Iteratives (★★★★✩) Example 9.2.3 Exercise 3: Tree Height (★★✩✩✩) Example 9.2.4 Exercise 4: Lowest Common Ancestor (★★★✩✩) Example 9.2.5 Exercise 5: Breadth-First (★★★✩✩) Examples 9.2.6 Exercise 6: Level Sum (★★★★✩) Example 9.2.7 Exercise 7: Tree Rotate (★★★✩✩) Example 9.2.8 Exercise 8: Reconstruction (★★★✩✩) Exercise 8a: Reconstruction from an Array (★★✩✩✩) Example Exercise 8b: Reconstruction from Preorder/Inorder (★★★✩✩) Example 9.2.9 Exercise 9: Math Evaluation (★★✩✩✩) Example 9.2.10 Exercise 10: Symmetry (★★✩✩✩) Examples Example 9.2.11 Exercise 11: Check Binary Search Tree (★★✩✩✩) Example 9.2.12 Exercise 12: Completeness (★★★★★) Exercise 12a: Number of Nodes (★✩✩✩✩) Example Exercise 12b: Check for Full / Perfect (★★✩✩✩) Example Exercise 12c: Completeness (★★★★✩) Example Exercise 12d: Completeness Recursive (★★★★★) Example 9.2.13 Exercise 13: Tree Printer (★★★★★) Example Exercise 13a: Width of a Subtree (★★✩✩✩) Examples Exercise 13b: Draw Node (★★✩✩✩) Example Exercise 13c: Draw Connection Lines (★★✩✩✩) Example Exercise 13d: Tree Representation (★★★★★) Example 9.3 Solutions 9.3.1 Solution 1: Tree Traversal (★★✩✩✩) Bonus: Fill Up a Tree into a List Verification 9.3.2 Solution 2: Preorder, Inorder, and Postorder Iteratives (★★★★✩) Example Verification Surprise Algorithm 9.3.3 Solution 3: Tree Height (★★✩✩✩) Example Verification 9.3.4 Solution 4: Lowest Common Ancestor (★★★✩✩) Example Verification 9.3.5 Solution 5: Breadth-First (★★★✩✩) Examples Verification 9.3.6 Solution 6: Level Sum (★★★★✩) Example Verification 9.3.7 Solution 7: Tree Rotate (★★★✩✩) Example Verification 9.3.8 Solution 8: Reconstruction (★★★✩✩) Solution 8a: Reconstruction from an Array (★★✩✩✩) Example Verification Solution 8b: Reconstruction from Preorder/Inorder (★★★✩✩) Example Verification 9.3.9 Solution 9: Math Evaluation (★★✩✩✩) Example Verification 9.3.10 Solution 10: Symmetry (★★✩✩✩) Examples Verification Bonus: Mirror Tree Example Verification 9.3.11 Solution 11: Check Binary Search Tree (★★✩✩✩) Example Verification 9.3.12 Solution 12: Completeness (★★★★★) Solution 12a: Number of Nodes (★✩✩✩✩) Example Solution 12b: Check for Full/Perfect (★★✩✩✩) Example Verification Solution 12c: Completeness (★★★★✩) Example Verification Solution 12d: Completeness Recursive (★★★★★) Example Verification 9.3.13 Solution 13: Tree Printer (★★★★★) Example Solution 13a: Width of a Subtree (★★✩✩✩) Examples Solution 13b: Draw Node (★★✩✩✩) Example Solution 13c: Draw Connection Lines (★★✩✩✩) Example Solution 13d: Tree Representation (★★★★★) Example Verification Chapter 10: Searching and Sorting 10.1 Introduction Search 10.1.1 Searching in Collections and Arrays Searching with contains() Searching with indexOf() and lastIndexOf() Programming Searches in Arrays Yourself 10.1.2 Binary Search with binarySearch() 10.2 Introduction Sort 10.2.1 Insertion Sort Determine Insertion Position Implementation of Insertion Sort 10.2.2 Selection Sort 10.2.3 Merge Sort 10.2.4 Quick Sort Inplace Implementation for Arrays 10.2.5 Bucket Sort 10.2.6 Final Thoughts 10.3 Exercises 10.3.1 Exercise 1: Contains All (★★✩✩✩) Examples 10.3.2 Exercise 2: Partitioning (★★★★✩) Examples Exercise 2a: Partitioning Two Letters (★★★✩✩) Exercise 2b: Partitioning Three Letters (★★★★✩) 10.3.3 Exercise 3: Binary Search (★★✩✩✩) Exercise 3a: Binary Search Recursive (★★✩✩✩) Examples Exercise 3b: Binary Search Iterative (★★✩✩✩) Examples 10.3.4 Exercise 4: Insertion Sort (★★✩✩✩) Example 10.3.5 Exercise 5: Selection Sort (★★✩✩✩) Example 10.3.6 Exercise 6: Quick Sort (★★★✩✩) Examples 10.3.7 Exercise 7: Bucket Sort (★★✩✩✩) Example 10.3.8 Exercise 8: Search in Rotated Data (★★★★✩) Exercise 8a: Flank Change Efficient (★★★★✩) Examples Exercise 8b: Binary Search in Rotated Data (★★★★✩) Examples 10.4 Solutions 10.4.1 Solution 1: Contains All (★★✩✩✩) Examples Verification 10.4.2 Solution 2: Partitioning (★★★✩✩) Examples Solution 2a: Partitioning Two Letters (★★✩✩✩) Solution 2b: Partitioning Three Letters (★★★✩✩) Verification 10.4.3 Solution 3: Binary Search (★★✩✩✩) Solution 3a: Binary Search Recursive (★★✩✩✩) Examples Solution 3b: Binary Search Iterative (★★✩✩✩) Examples Verification 10.4.4 Solution 4: Insertion Sort (★★✩✩✩) Example Verification 10.4.5 Solution 5: Selection Sort (★★✩✩✩) Example Verification 10.4.6 Solution 6: Quick Sort (★★★✩✩) Examples Verification 10.4.7 Solution 7: Bucket Sort (★★✩✩✩) Example Verification 10.4.8 Solution 8: Search in Rotated Data (★★★★✩) Solution 8a: Flank Change Efficient (★★★★✩) Examples Verification Solution 8b: Binary Search in Rotated Data (★★★★✩) Examples Verification Chapter 11: Conclusion and Supplementary Literature 11.1 Conclusion 11.1.1 Lessons Learned per Chapter 11.1.2 Noteworthy Thoughts on Maintainability Thoughts on Performance Advantages of Unit Tests 11.2 Puzzles 11.2.1 Gold Bags: Detect the Fake Solution 11.2.2 Horse Race: Determine Fastest Three Horses Solution 11.3 Supplementary Literature 11.3.1 Introduction to Algorithms and Data Structures 11.3.2 Basic Books 11.3.3 Specializing in Interview Questions 11.3.4 Supplements for Job Interviews at Top Companies Part III: Appendices Appendix A: Quick Start for JShell A.1 Java + REPL => jshell A.1.1 Introductory Example A.1.2 More Commands and Possibilities A.1.3 Using Syntactic Specialties and Modern Java Features A.1.4 More Complex Actions A.1.5 Exiting the JShell Appendix B: Short Introduction to JUnit 5 B.1 Writing and Running Tests B.1.1 Example: A First Unit Test B.1.2 Fundamentals of Writing and Running Tests Testing Multiple Assertions with assertAll() Test Execution Eclipse plugin MoreUnit B.1.3 Handling Expected Exceptions with assertThrows() B.2 Parameterized Tests with JUnit 5 B.2.1 Introduction to Parameterized Tests with JUnit 5 B.2.2 More Practical Parameterized Tests B.2.3 JUnit Parameterized Tests with @MethodSource Appendix C: Quick Start for O-notation C.1 Estimations with O-notation C.1.1 Complexity Classes C.1.2 Complexity and Program Running Time Bibliography Index "Expand your knowledge of Java with this entertaining learning guide, which features 100+ exercises and programming challenges. Java Challenges will prepare you for your next exam or job interview, and covers many practical topics, such as strings, arrays, data structures, recursion, and date and time. The APIs and other material included in this book are Java 17 compatible. Each topic is addressed in its own separate chapter, starting with an introduction to the basics and followed by multiple exercises of varying degrees of difficulty, helping you to improve your programming skills effectively. Detailed sample solutions, including the algorithms used for all tasks, are included to maximize your understanding of each area. Author Michael Inden also describes alternative solutions and analyzes possible pitfalls and typical errors. Three appendices round out the book: on covering JShell, which is often helpful for trying out the code snippets and examples in the book, followed by an introduction to JUnit 5 for unit testing and verifying solutions, while the final appendix explains O-notation for estimating performance. After reading this book, you'll be prepared to take the next step in your career or tackle your next personal project. All source code is freely available for download via the Apress website."-- Provided by publisher