Data Structures, Algorithms, Programming Concepts (C/C++/Python/Java), OOP & Web Development (Part 9)

Question 1

Why can the "Fractional Knapsack Problem" be solved optimally using a Greedy Algorithm, whereas the "0/1 Knapsack Problem" REQUIRES Dynamic Programming?

Accepted Answer

In Fractional Knapsack, items can be broken into fractional parts, making sorting by value-to-weight ratio optimal; in 0/1 Knapsack, items are indivisible, and greedy choices can leave empty wasted capacity

Answer

0/1 Knapsack has no numbers

Answer

Fractional Knapsack requires exponential time

Answer

0/1 Knapsack only works on arrays

Question 2

What are the two defining mathematical characteristics that a problem MUST possess to be solved using Dynamic Programming?

Accepted Answer

Optimal Substructure (optimal solution contains optimal solutions to subproblems) and Overlapping Subproblems (same subproblems are solved repeatedly)

Answer

Linear time complexity and small memory

Answer

Divide and conquer with sorting

Answer

Constant memory and binary search

Question 3

What is the time complexity to find the length of the Longest Common Subsequence (LCS) between two strings of lengths $M$ and $N$ using Dynamic Programming?

Accepted Answer

O(M * N)

Answer

O(2^(M+N))

Answer

O(M + N)

Answer

O(log(M * N))

Question 4

In the JavaScript asynchronous runtime architecture, how does the "Event Loop" prioritize between the "Microtask Queue" (Promises) and the "Callback / Task Queue" (`setTimeout`)?

Accepted Answer

The Event Loop executes ALL pending jobs in the Microtask Queue to completion BEFORE executing the next task from the Macro-task / Callback Queue

Answer

`setTimeout` always executes before Promises

Answer

Microtasks run only once every hour

Answer

Tasks in both queues execute randomly in parallel threads

Question 5

What is a "Closure" in JavaScript?

Accepted Answer

A function bundled together with references to its surrounding lexical environment, allowing an inner function to retain access to outer function variables even after the outer function has finished executing and returned

Answer

A method that closes the browser window

Answer

A tag that closes an HTML element

Answer

A tool that deletes temporary variables

Question 6

How does Object Inheritance work under JavaScript's "Prototypal Inheritance" model?

Accepted Answer

Objects have an internal hidden link (`[[Prototype]]` / `__proto__`) to another prototype object; when an attribute is accessed, JavaScript traverses up the "Prototype Chain" until it finds the property or reaches `null`

Answer

JavaScript copies all methods into every object instance in memory

Answer

Objects inherit through C++ classes

Answer

JavaScript does not support inheritance

Question 7

In REST API architectural standards, which of the following HTTP request methods is NOT "Idempotent"?

Accepted Answer

POST (executing multiple identical requests creates multiple distinct resources on the server)

Answer

GET

Answer

PUT

Answer

DELETE

Question 8

What is a "CORS Preflight Request" sent by web browsers?

Accepted Answer

An automated HTTP `OPTIONS` request sent by the browser before the actual cross-origin request to verify whether the target server permits the method and headers

Answer

A ping request testing internet speed

Answer

A request that downloads images

Answer

An authentication popup

Question 9

What is the primary architectural difference between CSS "Flexbox" and CSS "Grid" layouts?

Accepted Answer

Flexbox is designed for One-Dimensional layouts (either rows OR columns); CSS Grid is designed for Two-Dimensional layouts (rows AND columns simultaneously)

Answer

Grid is for mobile only; Flexbox is for desktop only

Answer

Flexbox requires JavaScript

Answer

CSS Grid cannot display images

Question 10

What are the two phases of "Event Propagation" in the DOM tree when an event (like a click) is triggered on a deeply nested button?

Accepted Answer

Capturing Phase (trickling down from `window` to the target element) followed by Bubbling Phase (bubbling up from the target element back to `window`)

Answer

Input Phase and Output Phase

Answer

Compile Phase and Execute Phase

Answer

Rendering Phase and Painting Phase

Question 11

What is the purpose of the "Promise.all()" method in JavaScript?

Accepted Answer

It takes an array of Promises and returns a single Promise that resolves when ALL input promises have resolved, or rejects immediately if ANY promise rejects

Answer

It runs promises sequentially one after another

Answer

It cancels all promises

Answer

It forces all promises to execute on the server

Question 12

What is "Just-In-Time" (JIT) compilation in modern JavaScript engines (such as Google Chrome's V8)?

Accepted Answer

A hybrid compilation strategy that monitors executing bytecode and dynamically compiles frequently executed "hot" functions directly into optimized native machine code at runtime

Answer

Compiling code exactly when the developer presses Save

Answer

An engine that translates JavaScript to Python

Answer

A memory garbage collection tool

Question 13

What is "Backtracking" in algorithm design (e.g. solving N-Queens or Sudoku)?

Accepted Answer

A recursive search technique that incrementally builds candidates for solutions and abandons (backtracks from) a candidate as soon as it determines the candidate cannot lead to a valid solution

Answer

Reversing an array in memory

Answer

Sorting numbers backward

Answer

Deleting history in a web browser

Question 14

What algorithmic paradigm and data structure does "Huffman Coding" use to generate optimal, lossless prefix-free compression codes based on character frequencies?

Accepted Answer

Greedy Algorithm using a Min-Priority Queue (Binary Min-Heap)

Answer

Dynamic Programming with an Array

Answer

Divide and Conquer with a Hash Map

Answer

Backtracking with a Stack

Question 15

What is a "Trie" (Prefix Tree) data structure, and what is its primary use case?

Accepted Answer

A tree data structure used for storing strings where each node represents a common character prefix, enabling fast O(L) string search, autocomplete, and spell checking (where L is string length)

Answer

A tree with exactly three child nodes per parent

Answer

A database index for numbers only

Answer

A binary heap used in operating systems