Arrays

Question 1

What is an array in C++?

Answer 1

Key: memory
Array: Chunk of memory

RAM ( Random Access Model ) model of computation

An array in C++ is a data structure used to store elements of the same type in sequential and indexed manner.

Question 2

How do you declare an array in C++?

Answer 2

int myArray[5];

Question 3

How do you initialize an array in C++?

Answer 3

An array can be initialized by providing a comma-separated list of elements within curly braces

int myArray[] = {1, 2, 3, 4, 5}; // static array
int *myArray = new int[10]; // dynamic array

Question 4

Explain the concept of contiguous memory allocation as it relates to arrays in C++

Answer 4

Contiguous memory allocation means that the elements of an array are stored in adjacent memory locations.
Imagine chunks of memory allocated near themselves, one by one. Where each element occupies a fixed-size memory slot.

It has elements in a fixed-size memory which are allocated side by side.

This allows to use indexing for efficient RAM.

Question 5

Discuss the difference between arrays and pointers in C++

Answer 5

Pointers point on the memory addresses.
Arrays store elements in a fixed-size memory.

Arrays and pointers are often confused, but they have distinct differences. Arrays are a fixed-size collection of elements of the same type stored in contiguous memory locations, while pointers are variables that store memory addresses. Arrays can decay into pointers when passed to functions or assigned to pointers, but they retain their size information.

Question 6

include <iostream></iostream>

Analyze the following C++ code snippet and explain its output:

using namespace std;

int main() {
int arr[3] = {1, 2, 3};
int* ptr = arr;

cout << *ptr << " ";   // Output: 1
cout << *(ptr + 1) << " ";  // Output: 2
cout << *(ptr + 2) << endl;  // Output: 3

return 0; }

Answer 6

This code snippet declares an integer array arr with 3 elements and initializes it.
Then, it declares a pointer ptr and assigns it the address of the first element of the array.
The cout statements dereference the pointer to print the values of the array elements sequentially. So, the output will be 1 2 3.

Question 7

Explain the concept of array decay in C++ and provide an example

Answer 7

Array decay refers to the automatic conversion of an array to a pointer to its first element in certain contexts, such as passing an array to a function or assigning it to a pointer variable.
For example:

void printArray(int arr[]) {
// Code to print array elements
}

int main() {
int myArray[5] = {1, 2, 3, 4, 5};
printArray(myArray); // Here, myArray decays into a pointer to its first element
return 0;
}

Question 8

Discuss the advantages and disadvantages of using arrays in C++ compared to other data structures.

Answer 8

ONE TYPE DATA STRUCTURE ALLOCATION
Vector gives us the opportunity to manage with data without worry about memory management, also gives us many useful functions.
Dynamic array allows us to direct memory access and to extend data structure methods. With amortization, adding elements to the end has constant time.
Static array has linear time in adding elements to the memory. Only getter and setter have constant time.
Linked lists are giving you time, they are better in adding and deleting elements from the beginning.

Question 9

Analyze the time complexity of accessing, inserting, and deleting elements in an array in C++.

Answer 9

Accessing elements in an array has constant time complexity O(1), as it involves simple arithmetic to calculate the memory address of the element.

Inserting and deleting elements in an array have time complexity O(n), as it may require shifting elements to maintain contiguous memory.

However, inserting or deleting at the end of the array can be done in constant time if sufficient space is available.

Question 10

Explain the difference between a static array and a dynamic array in C++

Answer 10

A dynamic array has a pointer to elements stored in a fixed-size memory, that can be dynamically resized as needed.

Question 11

What is a multi-dimensional array?

Answer 11

Each element is identified by multi indexes; it is like a matrix that has elements in the table, which has rows and columns.

Question 12

How does C++ handle array index out-of-bound errors?

Answer 12

You have to use static array with static size implementation, you can use also vector, that automatically manage memory.

Question 13

Discuss the advantages and disadvantages of using arrays over vectors in C++

Answer 13

Dynamic arrays benefits lies in management and development; it is data structure; solution.

Vector assigns for simplicity; it is ADT (Abstract Data Type/ Abstract Data Structure), interface; problem.

Question 14

How would you find the size of an array in C++?

Answer 14

int sizeOfArray = sizeof(array)/sizeof(array[0])

Question 15

Explain how you can pass an array to a function.

Answer 15

By reference or as a pointer;

Question 16

What is an array of pointers? Give an example of its usage.

Answer 16

Array of pointers has pointers as the elements. It can store for example objects

Question 17

How would you initialize an array of integers with all elements set to zero in C++?

Answer 17

int myArray[n] = {};
int* myArray = new intn;
delete[] myArray;

Question 18

What is the difference between passing an array to a function by value and by reference in C++?

Answer 18

By value, you will work on the copy of the array and by reference you will work on the actual elements allocated in fixed-size memory.

Question 19

Explain the concept of array decay in C++. When does it occur, and how does it affect function parameters?

Answer 19

You pass the first element of an array and the size of an array is lost. You can move from element to element, but you do not know the size.
Furthermore, you have to be aware of that problem, because you can leave the array.

Question 20

Discuss the time complexity of searching for an element in an unsorted array vs. a sorted array.

Answer 20

Unsorted: O(n)
Sorted: O(logn) (by binary search)

Question 21

What are the potential pitfalls of using arrays in C++?

Answer 21

Memory management

Question 22

How would you dynamically allocate memory for an array in C++? What considerations should be taken into account when using dynamic arrays?

Answer 22

int* dynArr = new int[10]; // Dynamic memory allocation
delete[] dynArr; // Freeing allocated memory

Question 23

Can you discuss some common algorithms or operations performed on arrays, such as sorting and traversing/searching?

Answer 23

traversing:
- linear
- reverse
- binary search

sorting:
- insert sort
- select sort
- bucket sort
- merge sort
- quick sort

Question 24

Which of the following statements correctly declares a dynamic array of integers in C++?

A) int* arr = new int[10];
B) int arr[10];
C) int* arr = new int(10);
D) int* arr = new int;

Answer 24

A

Question 25

Which of the following functions correctly finds the maximum element in an array myArray of integers in C++?

int myArray[] = {10, 20, 30, 40, 50};
A) int max = *std::max_element(myArray, myArray + 5);
B) int max = std::max(myArray);
C) int max = std::max_element(myArray, myArray + 5);
D) int max = *std::max(myArray);

Answer 25

A

Question 26

What is the time complexity of searching for an element in a sorted array of size n using binary search?

A) O(1)
B) O(n)
C) O(log n)
D) O(n log n)

Answer 26

C

Question 27

What happens if you attempt to access an element beyond the bounds of an array in C++?

A) The program throws a compilation error.
B) The program executes normally with no side effects.
C) The program may crash or exhibit undefined behavior.
D) The compiler automatically resizes the array.

Answer 27

C / garbage data

Question 28

Which statement correctly frees the memory allocated for a dynamic array arr in C++?
int* arr = new int[10];

A) free(arr);
B) delete arr;
C) delete[] arr;
D) delete[] arr[];

Answer 28

C

Question 29

What is the correct way to find the length of an array arr in C++?
int arr[] = {1, 2, 3, 4, 5};

A) int length = sizeof(arr);
B) int length = arr.size();
C) int length = sizeof(arr) / sizeof(arr[0]);
D) int length = arr.length();

Answer 29

C

Question 30

What is the difference in this two implementation for an array:
- malloc/free/realloc
- new/delete/for…loop

Answer 30

Malloc is better for smaller size array, for example of size 40, because malloc finds free bytes right after the allocated chunk of memory and in the difference to new it doesn’t have to always reallocate the full chunk of memory just add some additional space.

Question 31

What about making other data structures on dynamic array?

Answer 31

Do this but not directly, it means that you should use the same type of implementation but don’t use the other DS to build DS.
Just use the knowledge, not the notes.
And why? Because it is faster.