OpsHub Interview Guide

Approach: Iterative: use three pointers (prev, curr, next). Recursive: reverse rest of list, then adjust pointers.

Approach: Use slow and fast pointer technique. When fast reaches end, slow is at middle.

Approach: Use four boundaries (top, bottom, left, right). Shrink boundaries after each traversal direction.

Approach: Use in-order traversal (should be sorted) or validate with min/max bounds at each node.

Approach: Expand around center technique. Check both odd and even length palindromes from each position.

Approach: Encapsulation (data hiding), Inheritance (IS-A), Polymorphism (method overloading/overriding), Abstraction (hiding complexity).

Approach: Abstract class: partial implementation, single inheritance. Interface: contract only, multiple inheritance. Java 8+ allows default methods in interfaces.

Approach: Occurs in multiple inheritance when two parents have same method. Java uses interfaces with default method resolution rules.

Approach: Overloading: same name, different parameters (compile-time polymorphism). Overriding: same signature in child class (runtime polymorphism).

Approach: ArrayList: dynamic array, O(1) access, O(n) insert. LinkedList: doubly-linked, O(n) access, O(1) insert at known position.

Approach: SELECT column, COUNT(*) FROM table GROUP BY column HAVING COUNT(*) > 1

Approach: 1NF: atomic values, no repeating groups. 2NF: 1NF + no partial dependencies. 3NF: 2NF + no transitive dependencies.

Approach: DELETE: row-by-row, can rollback, fires triggers. TRUNCATE: all rows, cannot rollback, faster. DROP: removes table structure.

Approach: SELECT MAX(salary) FROM employees WHERE salary < (SELECT MAX(salary) FROM employees); or use LIMIT/OFFSET.

Approach: Atomicity (all or nothing), Consistency (valid state), Isolation (concurrent safety), Durability (permanent after commit).

Approach: REST: architectural style for web services. GET (read), POST (create), PUT (update), DELETE (remove), PATCH (partial update).

Approach: REST: lightweight, JSON/XML, stateless, uses HTTP. SOAP: protocol, XML only, built-in security (WS-Security), more overhead.

Approach: Maintains backward compatibility when API changes. Methods: URL path (/v1/), query param (?version=1), header (Accept-Version).

Approach: Push-based notifications. Server sends HTTP POST to client URL when event occurs. Used for real-time sync, event-driven systems.