Hi #codeforces

I have solved around 100 (800 rating) questions and 20 (900 rating) but when i solve a another 900 rating question i first get in doubt by seeing the long theory of question. somehow i make a courage to read and understand but then i ended up with not able make correct solution. sometimes i think whole diffrent approach as compare to ideal.

for example I was solving this clockwork question (900 rating) . i even did not understand the question. but when i see the solution i see same if else , loops , vectors use . thatm means i know using what problem can be solve but how to arrange these pieces is seems impossible.

what should i do any suggestion.

i code in c++

Here are all the Java topics from Core to Advanced (up to JDBC):

CORE JAVA

Introduction to Java

1. JDK, JRE, JVM
2. Data Types & Variables
3. Operators
4. Control Statements (if, else, switch)
5. Loops (for, while, do-while)
6. Arrays
7. Strings & String Methods
8. Methods & Method Overloading
9. Recursion

OBJECT-ORIENTED PROGRAMMING (OOP)

1. Classes & Objects
2. Constructors
3. this Keyword
4. Inheritance
5. Method Overriding
6. super Keyword
7. Polymorphism
8. Abstraction
9. Encapsulation
10. Interfaces
11. Abstract Classes
12. final Keyword
13. static Keyword
14. Instance & Static Blocks

PACKAGES & ACCESS MODIFIERS **** 24. Packages 25. Access Modifiers (public, private, protected, default) 26.import Statement

EXCEPTION HANDLING

1. Types of Errors
2. try, catch, finally
3. throw & throws
4. Custom Exceptions
5. Checked & Unchecked Exceptions

JAVA I/O

1. Scanner Class
2. BufferedReader
3. File Handling (File, FileReader, FileWriter)
4. BufferedReader & BufferedWriter
5. Serialization & Deserialization

COLLECTIONS FRAMEWORK

1. List (ArrayList, LinkedList)
2. Set (HashSet, LinkedHashSet, TreeSet)
3. Map (HashMap, LinkedHashMap, TreeMap)
4. Queue & Deque
5. Iterator & ListIterator
6. Collections Utility Class
7. Comparable & Comparator

GENERICS

1. Generic Classes
2. Generic Methods
3. Bounded Type Parameters
4. Wildcards

MULTITHREADING

1. Thread Class & Runnable Interface
2. Thread Life Cycle
3. Thread Methods (sleep, join, yield)
4. Synchronization
5. Inter-thread Communication (wait, notify, notifyAll)
6. Deadlock
7. Executor Framework

ADVANCED JAVA

1. Lambda Expressions
2. Functional Interfaces
3. Stream API & Regex
4. Optional Class
5. Method References
6. Default & Static Methods in Interface
7. Var Keyword
8. Sealed Classes (Java 17+)
9. Records (Java 16+)
10. Text Blocks

JAVA 8+ FEATURES

1. Date & Time API (LocalDate, LocalTime, LocalDateTime)
2. forEach & removeIf
3. Map.Entry iteration

INNER CLASSES

1. Static Nested Class
2. Inner Class
3. Local Class
4. Anonymous Class

JDBC (Java Database Connectivity)

1. JDBC Architecture & Drivers
2. Connecting to Database (MySQL/Oracle)
3. Statement, PreparedStatement, CallableStatement
4. ResultSet & ResultSetMetaData
5. CRUD Operations using JDBC
6. Transaction Management (commit, rollback)
7. Batch Processing
8. Connection Pooling (DataSource)
9. Stored Procedures with JDBC