Data Structures, Algorithms, Programming Concepts (C/C++/Python/Java), OOP & Web Development (Part 5)

Question 1

What is the difference between "Call by Value" and "Call by Reference" in parameter passing?

Accepted Answer

Call by Value passes a copy of the actual argument value (changes inside the function do NOT affect the caller); Call by Reference passes the memory address/reference (changes inside the function directly alter the caller's variable)

Answer

Call by Value is for pointers only

Answer

Call by Reference is unsupported in C++

Answer

Call by Value is faster for large structures

Question 2

What is the essential component required in every recursive function to prevent an infinite recursion loop and eventual Stack Overflow crash?

Accepted Answer

Base Case (Termination condition)

Answer

A global pointer

Answer

A `for` loop

Answer

A `malloc()` call

Question 3

What is a "Copy Constructor" in C++?

Accepted Answer

A special constructor used to initialize a newly created object as a copy of an existing object of the same class (e.g. `ClassName(const ClassName &source)`)

Answer

A constructor that copies files to disk

Answer

A tool that duplicates code in the editor

Answer

A constructor that takes zero arguments

Question 4

What is the famous "Diamond Problem" in object-oriented multiple inheritance, and how does C++ resolve it?

Accepted Answer

Ambiguity arising when a class inherits from two classes that both inherit from a common base class (inheriting duplicate copies of base members); resolved in C++ using "Virtual Base Classes" (`virtual public Base`)

Answer

A hardware GPU rendering bug

Answer

A database deadlocking issue

Answer

An algorithm for diamond sorting

Question 5

What is the difference between "Function Overloading" (Compile-time Polymorphism) and "Method Overriding" (Run-time Polymorphism)?

Accepted Answer

Function Overloading defines multiple functions with the same name but different parameter lists within the same class; Method Overriding redefines a base class virtual method in a derived subclass with the exact same signature

Answer

Overloading is for virtual functions only

Answer

Overriding occurs at compile time

Answer

They are exact synonyms

Question 6

How does the C++ runtime execute Dynamic Method Dispatch for virtual functions?

Accepted Answer

Using a Virtual Method Table (`vtable`) containing pointers to virtual functions, where each object contains a hidden Virtual Table Pointer (`vptr`) pointing to its class `vtable`

Answer

By scanning the source code file at runtime

Answer

By running an automatic interpreter loop

Answer

By rebooting the thread

Question 7

What makes a C++ class an "Abstract Class" that CANNOT be directly instantiated into objects?

Accepted Answer

It contains at least ONE "Pure Virtual Function" (declared with `= 0`, e.g. `virtual void draw() = 0;`)

Answer

It has no public variables

Answer

It contains only integer constants

Answer

It has no destructor

Question 8

In C++, what is the difference between `private` and `protected` class members?

Accepted Answer

`private` members can be accessed ONLY within the class where they are defined; `protected` members can be accessed within the defining class AND by derived subclasses

Answer

`protected` members are accessible to all external code

Answer

`private` members can be inherited without restrictions

Answer

They are exact synonyms in C++

Question 9

Why does Java support multiple inheritance of "Interfaces" (`implements A, B`), but strictly forbids multiple inheritance of "Classes" (`extends A, B`)?

Accepted Answer

To eliminate the Diamond Problem and state ambiguity while allowing classes to implement multiple behavioral contracts

Answer

Because interfaces do not use memory in Java

Answer

Because Java is a 16-bit language

Answer

To speed up garbage collection

Question 10

In Java, what is the effect of applying the `final` keyword to a Variable, a Method, and a Class, respectively?

Accepted Answer

Variable: becomes a constant; Method: cannot be overridden by subclasses; Class: cannot be inherited (subclassed)

Answer

Variable: is deleted; Method: runs in parallel; Class: becomes abstract

Answer

All three are converted into bytecode

Answer

Variable: becomes public; Method: runs faster; Class: becomes an interface

Question 11

What is the output of the Python list comprehension `[x**2 for x in range(5) if x % 2 == 0]`?

Accepted Answer

[0, 4, 16]

Answer

[0, 1, 4, 9, 16]

Answer

[1, 9]

Answer

[4, 16]

Question 12

In Python class definitions, what is the purpose of the `__init__()` method and the `self` parameter?

Accepted Answer

`__init__()` is the constructor method automatically invoked upon object instantiation; `self` represents the instance of the class allowing access to its attributes and methods

Answer

`__init__()` destroys the object from RAM; `self` is a reserved global variable

Answer

`__init__()` is for importing libraries

Answer

`self` compiles Python code to C++

Question 13

In a 2D array $A[M][N]$ stored in "Row-Major Order" in memory with base address $B$ and element size $W$ bytes, what is the formula to calculate the memory address of element $A[i][j]$ (assuming 0-based indexing)?

Accepted Answer

Address(A[i][j]) = B + (i * N + j) * W

Answer

Address(A[i][j]) = B + (j * M + i) * W

Answer

Address(A[i][j]) = B + (i + j) * W

Answer

Address(A[i][j]) = B + i * j * W

Question 14

What is the Postfix (Reverse Polish Notation) equivalent of the Infix arithmetic expression: `(A + B) * C - D / E`?

Accepted Answer

A B + C * D E / -

Answer

A B C + * D E / -

Answer

- * + A B C / D E

Answer

A B + * C D E / -

Question 15

Evaluating the Postfix expression `5 3 + 2 * 4 -` using a Stack yields which final numerical result?

Accepted Answer

12

Answer

16

Answer

10

Answer

6