Data Structures, Algorithms, Programming Concepts (C/C++/Python/Java), OOP & Web Development (Part 10)

Question 1

In C/C++, what does the bitwise trick `x & (x - 1)` compute on a positive integer $x$?

Accepted Answer

It clears (turns to 0) the lowest / rightmost set bit (1-bit) of $x$ (used to count set bits and test if a number is a power of 2)

Answer

It doubles the value of $x$

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It calculates the square of $x$

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It flips all bits of $x$

Question 2

How do "Union by Rank" and "Path Compression" optimize Disjoint Set Union (DSU / Union-Find) operations?

Accepted Answer

They flatten tree depths and attach smaller trees under deeper roots, reducing the amortized time complexity of `find` and `union` operations to nearly constant time O(α(N)) (Inverse Ackermann function)

Answer

They convert the graph to an array

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They delete duplicate edges

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They eliminate the need for pointers

Question 3

In modern C++ (C++11+), what is the difference between `std::unique_ptr` and `std::shared_ptr` in RAII memory management?

Accepted Answer

`std::unique_ptr` enforces exclusive single ownership of a dynamically allocated object (cannot be copied, only moved); `std::shared_ptr` maintains a reference count allowing multiple pointers to share ownership, automatically freeing memory when the reference count reaches 0

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`std::unique_ptr` is stored on the stack; `std::shared_ptr` is in the database

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`std::shared_ptr` is for integers only

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`std::unique_ptr` cannot be deleted

Question 4

What is "Kahn's Algorithm" for Topological Sorting?

Accepted Answer

An algorithm that calculates the In-Degree of every vertex, pushes all vertices with In-Degree 0 into a Queue, and repeatedly dequeues vertices while decrementing neighbor in-degrees

Answer

An algorithm that sorts edges alphabetically

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A shortest path algorithm for negative cycles

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A graph coloring algorithm

Question 5

How does the "WebSocket" protocol (RFC 6455) differ from traditional HTTP communications?

Accepted Answer

WebSockets establish a persistent, full-duplex, bidirectional TCP communication channel over a single socket connection, allowing the server to push real-time data to the client with minimal header overhead

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WebSockets work only without internet connectivity

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WebSockets can only transmit static HTML files

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WebSockets require optical fiber connections

Question 6

What is the primary difference between `localStorage` and `sessionStorage` in modern Web Storage APIs?

Accepted Answer

`localStorage` data persists indefinitely with no expiration time even after closing and reopening the browser; `sessionStorage` data is cleared automatically when the specific browser tab or session is closed

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`localStorage` stores data on the server; `sessionStorage` stores in RAM

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`sessionStorage` can hold up to 50 GB; `localStorage` holds 1 KB

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`localStorage` requires a database password

Question 7

What is a "Service Worker" in Progressive Web Apps (PWAs)?

Accepted Answer

A client-side programmable JavaScript network proxy that runs in the background separate from the main browser thread, intercepting network requests, managing caches, and enabling offline functionality and push notifications

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A server administrator who manages cloud hardware

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A database script that cleans log files

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A background audio player

Question 8

What are "Sass" and "LESS" in frontend web development?

Accepted Answer

CSS Preprocessors that extend standard CSS with variables, nested rules, mixins, functions, and mathematical operators, compiling down into standard CSS for browser rendering

Answer

JavaScript libraries for 3D gaming

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HTML template validators

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Web server software programs

Question 9

What is the purpose of adding `'use strict';` at the top of a JavaScript file or function?

Accepted Answer

It enforces Strict Mode, catching common coding errors (such as preventing accidental creation of global variables, disallowing duplicate parameter names, and eliminating silent errors by throwing exceptions)

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It encrypts the JavaScript code

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It converts JavaScript into TypeScript

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It speeds up network download speeds

Question 10

What is "Currying" in functional programming and JavaScript?

Accepted Answer

A technique of transforming a function that takes multiple arguments $f(a, b, c)$ into a sequence of nested unary functions that each take a single argument: $f(a)(b)(c)$

Answer

A method of cooking Indian curry using code

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An algorithm for sorting arrays in parallel

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A database normalization technique

Question 11

What is the "Shadow DOM" in Web Components standard?

Accepted Answer

An encapsulated, isolated DOM sub-tree attached to an element whose internal styles and HTML structure are hidden and scoped, preventing external CSS styles from leaking in or out

Answer

A dark theme for web browsers

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A backup copy of the DOM stored on the server

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A visual drop-shadow effect in CSS

Question 12

What is a "Segment Tree" data structure, and what query operations does it optimize?

Accepted Answer

A binary tree used for storing intervals/segments, enabling Range Queries (Range Sum, Range Minimum) and Point Updates in O(log N) time

Answer

A tree used exclusively for sorting strings

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A tree that segments memory pages in operating systems

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A linear linked list

Question 13

What is a "Binary Indexed Tree" (BIT / Fenwick Tree)?

Accepted Answer

An array-based data structure that efficiently computes Prefix Sums and updates array frequencies in O(log N) time using bitwise two's complement operations (`i += i & (-i)`)

Answer

A binary search tree with colored nodes

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A database indexing structure for B-trees

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A hardware chip for floating-point calculations

Question 14

What is the time complexity of the "Knuth-Morris-Pratt" (KMP) pattern matching algorithm for searching a pattern of length $M$ inside a text of length $N$?

Accepted Answer

O(N + M) (linear time, utilizing a Longest Prefix Suffix / LPS array to avoid backtracking in the text)

Answer

O(N * M)

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O(N^2)

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O(log(N + M))

Question 15

In computational complexity theory, what defines an "NP-Complete" problem (e.g. Traveling Salesperson Problem, Boolean 3-SAT, Vertex Cover)?

Accepted Answer

A problem that is in NP (a candidate solution can be verified in Polynomial time) and is NP-Hard (every problem in NP can be reduced to it in polynomial time); if ANY NP-Complete problem has a polynomial-time solution, then P = NP

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A problem that cannot be solved by any computer even in infinite time

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A problem with a linear time complexity O(N)

Answer

A program with a syntax error

Data Structures, Algorithms, Programming Concepts (C/C++/Python/Java), OOP & Web Development (Part 10)

In C/C++, what does the bitwise trick `x & (x - 1)` compute on a positive integer xxx?

In C/C++, what does the bitwise trick `x & (x - 1)` compute on a positive integer $x$ ?