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Questions and Answers
What operator is used to allocate memory for a block of objects in dynamic arrays?
What operator is used to allocate memory for a block of objects in dynamic arrays?
- malloc
- alloc
- new (correct)
- calloc
A static array must have its size determined at runtime.
A static array must have its size determined at runtime.
False (B)
In dynamic data structures, where do the elements of a vector reside?
In dynamic data structures, where do the elements of a vector reside?
heap
To create a dynamic array of objects of type T with length n, the expression is new T[____].
To create a dynamic array of objects of type T with length n, the expression is new T[____].
Match the following terms with their definitions:
Match the following terms with their definitions:
Which operation retrieves an element from a vector?
Which operation retrieves an element from a vector?
The size of a vector can remain constant during its lifetime.
The size of a vector can remain constant during its lifetime.
What does the push_back operation do in a vector?
What does the push_back operation do in a vector?
A contiguous part of memory allocated for storing dynamic arrays is referred to as an _______.
A contiguous part of memory allocated for storing dynamic arrays is referred to as an _______.
What is the result of allocating every element of a vector separately?
What is the result of allocating every element of a vector separately?
What does the new T[] operator return?
What does the new T[] operator return?
Pointer arithmetic allows you to access elements beyond the bounds of the array.
Pointer arithmetic allows you to access elements beyond the bounds of the array.
What segments of memory does a pointer point to when using the new T[] operator?
What segments of memory does a pointer point to when using the new T[] operator?
To access the third element of an array pointed to by pointer p, you would use *(p + ______).
To access the third element of an array pointed to by pointer p, you would use *(p + ______).
Match the pointer expressions with their corresponding descriptions.
Match the pointer expressions with their corresponding descriptions.
If int* p = new int[n]; how do you access the value of the second element?
If int* p = new int[n]; how do you access the value of the second element?
The expression p + 3 directly gives you the address of the first element in the array.
The expression p + 3 directly gives you the address of the first element in the array.
In the context of pointer arithmetic, what does 'p + i' represent?
In the context of pointer arithmetic, what does 'p + i' represent?
If p points to an integer array of size n, then p + n points to ______.
If p points to an integer array of size n, then p + n points to ______.
What happens if you try to access *(p + n)?
What happens if you try to access *(p + n)?
What is the purpose of the push_back operation in a vector?
What is the purpose of the push_back operation in a vector?
The new operator is used to allocate memory for a fixed size array at compile time.
The new operator is used to allocate memory for a fixed size array at compile time.
What does the expression *(p + i) yield?
What does the expression *(p + i) yield?
The chunk of memory allocated for dynamic arrays is called an __________.
The chunk of memory allocated for dynamic arrays is called an __________.
Match the following pointer expressions with their descriptions:
Match the following pointer expressions with their descriptions:
What is the value of *(p + 2) if int* p = new int[5] and we initially set the array values to {10, 20, 30, 40, 50}?
What is the value of *(p + 2) if int* p = new int[5] and we initially set the array values to {10, 20, 30, 40, 50}?
Pointer arithmetic allows access to elements only within the bounds of the allocated array.
Pointer arithmetic allows access to elements only within the bounds of the allocated array.
A vector is a static data structure that must have its size determined at compile time.
A vector is a static data structure that must have its size determined at compile time.
What is the expression used to allocate a new array of size n for type T?
What is the expression used to allocate a new array of size n for type T?
In pointer arithmetic, the expression *(p + i) yields the value of the ______ element.
In pointer arithmetic, the expression *(p + i) yields the value of the ______ element.
Match the following pointer operations with their effects:
Match the following pointer operations with their effects:
After allocating an array with the expression int* p = new int[5], what will p + 2 point to?
After allocating an array with the expression int* p = new int[5], what will p + 2 point to?
Pointer arithmetic allows you to access elements beyond the allocated memory of an array.
Pointer arithmetic allows you to access elements beyond the allocated memory of an array.
What type of pointer is returned when using the new T[n] expression?
What type of pointer is returned when using the new T[n] expression?
By using the expression new T[____], a contiguous block of memory can be allocated dynamically.
By using the expression new T[____], a contiguous block of memory can be allocated dynamically.
Match the following components of a vector with their descriptions:
Match the following components of a vector with their descriptions:
What must be done before accessing an array's elements?
What must be done before accessing an array's elements?
Arrays can be copied directly using assignment.
Arrays can be copied directly using assignment.
What operator is used to delete a dynamically allocated array?
What operator is used to delete a dynamically allocated array?
When using arrays, the programmer must ensure that the indices do not go __________.
When using arrays, the programmer must ensure that the indices do not go __________.
Match the programming commands with their descriptions:
Match the programming commands with their descriptions:
What happens if you attempt to access an index that is out of the array's bounds?
What happens if you attempt to access an index that is out of the array's bounds?
The length of an array must be specified at runtime.
The length of an array must be specified at runtime.
What is the initial value of array indices in programming?
What is the initial value of array indices in programming?
In pointer arithmetic, to access the fifth element using pointer p, you would use *(p + __________).
In pointer arithmetic, to access the fifth element using pointer p, you would use *(p + __________).
Match the following array operations with their results:
Match the following array operations with their results:
Flashcards
Allocating memory for a single object
Allocating memory for a single object
Allocating memory for a single object using the new operator.
Allocating a block of memory
Allocating a block of memory
Allocating a contiguous block of memory for multiple objects of the same type.
Dynamic data structure
Dynamic data structure
A data structure that allows elements to be added or removed during runtime, providing a flexible way to manage data.
Random access
Random access
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Dynamic array
Dynamic array
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Size of a dynamic array
Size of a dynamic array
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Contiguous memory for a dynamic array
Contiguous memory for a dynamic array
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Appending an element
Appending an element
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Getting an element from a dynamic array
Getting an element from a dynamic array
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Setting an element in a dynamic array
Setting an element in a dynamic array
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Creating an array using new T[n]
Creating an array using new T[n]
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Pointer returned by new T[n]
Pointer returned by new T[n]
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Pointer Arithmetic
Pointer Arithmetic
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End of Array Pointer
End of Array Pointer
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Dereference Operator (*)
Dereference Operator (*)
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Accessing the Second Element
Accessing the Second Element
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Accessing the Last Element
Accessing the Last Element
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Contiguous Memory
Contiguous Memory
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Efficiency of Pointer Arithmetic
Efficiency of Pointer Arithmetic
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Pointer Arithmetic Bounds
Pointer Arithmetic Bounds
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What is a vector?
What is a vector?
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How does new T[expr] allocate memory for an array?
How does new T[expr] allocate memory for an array?
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What is pointer arithmetic and how does it work?
What is pointer arithmetic and how does it work?
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What does the new operator return?
What does the new operator return?
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How to represent the end of an array using pointer arithmetic?
How to represent the end of an array using pointer arithmetic?
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How to access elements within an array using pointer arithmetic?
How to access elements within an array using pointer arithmetic?
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What is the sizeof operator used for?
What is the sizeof operator used for?
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How to release memory allocated using new?
How to release memory allocated using new?
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What does the delete[] operator do?
What does the delete[] operator do?
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What is a memory leak?
What is a memory leak?
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Accessing an Array Element using Pointer Arithmetic
Accessing an Array Element using Pointer Arithmetic
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Releasing Memory Allocated using new
Releasing Memory Allocated using new
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Memory Leaks
Memory Leaks
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What is an array?
What is an array?
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How do I access an array element?
How do I access an array element?
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How do I copy arrays?
How do I copy arrays?
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What is a dynamic array?
What is a dynamic array?
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How do I allocate a dynamic array?
How do I allocate a dynamic array?
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How do I release a dynamic array?
How do I release a dynamic array?
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What is a pointer?
What is a pointer?
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What is pointer arithmetic?
What is pointer arithmetic?
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How do I access an array element using a pointer?
How do I access an array element using a pointer?
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What happens if I don't release dynamically allocated memory?
What happens if I don't release dynamically allocated memory?
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Study Notes
Introduction to Computer Science Course Information
- Course code: 252-0032, 252-0047, 252-0058
- Authors: Manuela Fischer and Felix Friedrich
- Department: Computer Science, ETH Zurich
- Semester: Fall 2024
Dynamic Data Structures II, Section 17
- Dynamic allocation of memory for objects using 'new'
- Implementing a vector class named 'our_vector' (equivalent to std::vector
) - Vectors allow dynamic resizing
- Memory contiguity in vectors
- Dynamic arrays
- Allocating memory chunks using
new T[n]for n objects of type T - Pointer arithmetic
- Adding an integer to a pointer
- Pointer differences
- Subtracting an integer from a pointer
- Pointer difference to calculate the distance between elements in an array
- Using
delete[]to release allocated memory - Implementing a destructor for the
our_vectorclass to free dynamically allocated memory. - The "Rule of Three" : For
our_vector, the destructor needs to be correctly defined along with a copy constructor and a copy assignment operator to prevent memory errors. - Copy Constructor, deep copy using
new[]to allocate space for a copy of the array andcopythe elements; deallocate withdelete[] - Assignment operator, copy-and-swap idiom avoiding self-assignment
- Prepend and Append Operations, insertion/deletion that require potentially expensive memory reallocation
Pointer Arithmetic and Arrays
- Pointer arithmetic involves adding and subtracting integers to/from pointers, altering memory addresses.
p + i(wherepis a pointer andiis an integer) points to theith element after the element pointed to byp.- Integer arithmetic is different from pointer arithmetic. Adding an integer to a pointer results in calculating a new address based on the size (in bytes) of the type being pointed to.
*(p + i)is used to access the element at the i-th position from the pointerp- Accessing the last element
p[n]- note thatp + nis one element past the last element. - Using the subscript operator
[]which is equivalent to*(p + i). - Subtracting a number from a pointer, calculating the difference between pointers. A pointer difference (p₁ - p₂) calculates the distance in indexes of the elements pointed to by p₁ & p₂ (only valid if p1 and p2 point into the same array or refer to elements in consecutive memory locations).
Iteration over an Array
- Iterating using sequential pointer iteration (e.g.,
for (char* it = p; it != p + 3; ++it), dereferencing and incrementing). - Index-based random access (e.g.,
for (int i = 0; i < 3; ++i)).
Arrays in Functions
- Passing arrays using pointers to the beginning and end of the array segment, e.g.,
beginandend, representing the first and one-past-the-last elements. - Using pointer notation with arrays: [begin, end).
Array-Based Vector Class
- Implementing a custom dynamic array class named
our_vector, handling memory allocation and management, including dynamic resizing. size()function returns the current size of the vector.operator[]to support element access using array notation. This should be overloaded for both non-constant and constant vectors.at(int i)often used for bounds checking.
Memory Management with Dynamic Arrays
- Vectors require dynamic memory management to grow/shrink
- When inserting/deleting in the middle of the vector, other elements need to be shifted in memory (expensive operation).
- To avoid frequent memory reallocation during insertion or deletion, vectors often allocate more memory than needed (resizing).
- Important: When allocating memory with
new[], deallocate it withdelete[]in the destructor to prevent memory leaks.
Insert and Remove Elements
- Implementing functions
push_front,push_back, andremovefor inserting and deleting elements. These potentially involve expensive memory reallocation due to contiguous memory layout. - These functions deal with memory reallocation for efficiency, given contiguous memory is in use.
- Vector operations that change size are costly since contiguous memory is in use.
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Description
Test your knowledge on dynamic data structures focusing on memory management and pointer arithmetic. This quiz covers the implementation of a vector class and the nuances of dynamic memory allocation using 'new'. Enhance your understanding of how vectors handle memory and pointers in C++.
