Q251. Explain dynamic programming and when to apply it.
DP solves problems with overlapping subproblems and optimal substructure by storing results and reusing them. Two styles: - Top-down memoisation: recursion plus a cache, ...
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Q252. How does the Java memory model and garbage collection work?
Memory is divided into heap (shared objects) and per-thread stacks (frames, locals). The heap has a young generation (Eden plus two survivor spaces) and an old generation...
Q253. Which is NOT a valid SQL command: SELECT, REMOVE, UPDATE, INSERT?
**REMOVE** is not valid. To delete rows, use `DELETE`. `DROP` removes objects (tables, databases). | Command | Purpose | |---------|---------| | SELECT | Read data | | IN...
Q254. Explain middleware in Express.
Middleware are functions with the signature (req, res, next) that run in order and can inspect or modify the request/response, end the cycle, or pass control with next()....
Q255. What is the GIL and how does it affect concurrency?
The Global Interpreter Lock is a mutex in CPython that allows only one thread to execute Python bytecode at a time. Consequences: - CPU-bound multithreading does not get ...
Q256. What are PHP 8 features you use regularly?
- Named arguments: htmlspecialchars(string: $s, flags: ENT_QUOTES). - Constructor property promotion and readonly properties. - Match expression (strict comparison, retur...
Q257. How does CSS specificity work and how do you resolve conflicts?
Specificity ranks selectors as (inline, IDs, classes/attributes/pseudo-classes, elements/pseudo-elements). Higher wins; equal specificity falls back to source order (late...
Q258. How do you narrow a union type?
Narrowing reduces a union to a subset within a control-flow branch. Techniques: - typeof for primitives. - instanceof for classes. - The in operator for property presence...
Q259. What is JSON and its common operations?
**JSON (JavaScript Object Notation)** is a lightweight, text-based data format that uses JavaScript object syntax for structuring data. It was popularized by Douglas Croc...
Q260. What is the difference between an Element and a Component?
**Element:** - A React **Element** is a plain JavaScript object that describes what you want to see on the UI. It represents a DOM node or a component at a specific point...