Ace Your Next Interview: Top 16 C++ Interview Questions and How to Answer Them.
C++ is a powerful programming language with a wide range of applications, and it is essential to have a solid understanding of the language to excel as a developer. Interviewers often ask a variety of questions to test a candidate’s knowledge of C++, including questions about basic concepts such as data types, control structures, and functions, as well as more advanced topics such as memory management, exception handling, and object-oriented programming.
Some of the top interview questions in C++ include questions about classes and objects, templates, exception handling, and memory management. Understanding the difference between a shallow copy and a deep copy is important when working with C++ objects, and knowing how to properly handle exceptions can help prevent errors in your code.
Additionally, understanding the difference between a vector and an array, and a function and a method in C++ is also important for effective coding. Furthermore, understanding the concepts of data structures such as Linked List, Hash Tables, and Binary Trees also becomes important in real-world applications.
Top 16 C++ Interview Questions
So these are some top 16 interviews question in C++
- What is the difference between C and C++?
- What is the difference between a class and a struct in C++?
- What is the difference between a constructor and a destructor in C++?
- Can you explain the concept of inheritance in C++?
- What is the difference between a stack and a queue in C++?
- What is the difference between a shallow copy and a deep copy in C++?
- How do you implement a linked list in C++?
- Can you explain the concept of exception handling in C++?
- What is the difference between a vector and an array in C++?
- What is the difference between a function and a method in C++?
- How do you implement a hash table in C++?
- Can you explain the concept of memory management in C++?
- What is the difference between a static and a dynamic library in C++?
- What is the difference between pass-by-value and pass-by-reference in C++?
- How do you implement a binary tree in C++?
- Can you explain the concept of operator overloading in C++?
let’s answer these question’s in detail one by one 🙂
Top 16 C++ Interview Questions with their answers
- What is the difference between C and C++?
C and C++ are both programming languages, but they have some key differences. C is a procedural programming language, which means it is based on a sequence of procedures or instructions for the computer to follow.
It is widely used for systems programming and embedded systems. C++, on the other hand, is an object-oriented programming language, which means it is based on the concept of objects that have certain properties and methods. It is an extension of C, and it has all the features of C, but also has additional features such as classes, objects, inheritance, and polymorphism.
C++ also supports function overloading, templates, and exception handling which are not present in C. C++ is widely used for developing large-scale applications such as video games, desktop applications, and operating systems.
- What is the difference between a class and a struct in C++?
In C++, a class and a struct are both user-defined data types that can contain data members and member functions. However, there are some key differences between the two:
- Default accessibility: In a class, the default accessibility of members is private, while in a struct it is public. This means that by default, members of a class can only be accessed by other members of the class, while members of a struct can be accessed by any code.
- Syntax: The syntax for defining a class and a struct is slightly different. A class is defined using the keyword “class”, and a struct is defined using the keyword “struct”.
- Inheritance: In C++, classes can inherit from other classes and can be inherited by other classes. Structs do not support inheritance.
- Semantic: The main semantic difference between class and struct is that class is a blueprint for creating objects (a class describes the properties and behaviors an object should have), while struct is a way of grouping data together.
In general, classes are used for objects that have more complex behavior and encapsulation, while structs are used for simple data structures that only need to hold data with no specific behavior.
- What is the difference between a constructor and a destructor in C++?
In C++, a constructor and a destructor are both special member functions of a class, but they serve different purposes.
A constructor is a special member function that is called when an object of a class is created. It is used to initialize the object and allocate memory. A constructor can have different parameters which are passed when creating an object of the class. The constructor is used to set the initial state of the object, it could also allocate memory for variables that are part of the class.
A destructor, on the other hand, is a special member function that is called when an object of a class is destroyed. It is used to deallocate memory and perform other cleanup tasks. A destructor does not have any parameters and it doesn’t return any values. The destructor is used to release resources that the object holds before it is destroyed.
Both constructors and destructors are called implicitly. Constructors are called when an object is created, and destructors are called when an object is destroyed. However, constructors can also be called explicitly using the “new” operator, and destructors can be called explicitly using the “delete” operator.
In summary, constructors are used to initializing the object and allocate memory, while destructors are used to deallocate memory and perform other cleanup tasks.
- Can you explain the concept of inheritance in C++?
In C++, inheritance is a mechanism that allows a class to inherit properties and methods from another class. It is a way of creating a hierarchy of classes, where a derived class inherits the properties and methods of the base class. Inheritance allows for the reuse of code and the creation of a more organized and efficient codebase.
A base class is also known as a parent class or superclass, while a derived class is also known as a child class or subclass. A derived class can inherit all or some of the members of the base class, including data members and member functions. A derived class can also add new members and methods of its own.
The main advantage of inheritance is that it allows for the reuse of code, which makes the development process faster and less error-prone. It also allows for the creation of a more organized and efficient codebase, by breaking down complex problems into smaller, more manageable parts.
There are two main types of inheritance in C++: single inheritance and multiple inheritances. Single inheritance is when a class inherits from only one base class, while multiple inheritances is when a class inherits from multiple base classes.
In summary, inheritance is a mechanism that allows a class to inherit properties and methods from another class, it allows for the reuse of code and the creation of a more organized and efficient codebase.
- What is polymorphism in C++?
In C++, polymorphism is the ability of a single function or operator to work with multiple types of data. It allows for the creation of generic functions and classes that can be used with a variety of data types. There are two types of polymorphism in C++: Compile-time polymorphism (also known as function overloading) and run-time polymorphism (also known as virtual functions).
Compile-time polymorphism, also known as function overloading, is when multiple functions have the same name but different parameters. The correct function to be called is determined at compile-time based on the types of arguments passed to the function. This is done by the compiler by checking the function signature which includes the name of the function and the type and number of its parameters.
Run-time polymorphism, also known as virtual functions, is when a base class pointer or reference is used to call a function that is overridden in the derived class. The correct function to be called is determined at run-time based on the type of object being pointed to or referred to. This is done by the use of virtual functions, where a virtual keyword is added to the base class function signature.
In summary, polymorphism is the ability of a single function or operator to work with multiple types of data, which allows for the creation of generic functions and classes that can be used with a variety of data types. It exists in two forms, compile-time polymorphism, and run-time polymorphism.
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- What is the difference between a stack and a queue in C++?
In C++, a stack and a queue are both data structures that store a collection of elements, but they have some key differences.
A stack is a data structure that follows the Last In First Out (LIFO) principle, meaning that the last element added to the stack is the first one to be removed. It can be implemented using an array or a linked list. The basic operations that can be performed on a stack include push, pop, and peek. The push operation adds an element to the top of the stack, the pop operation removes the top element from the stack, and the peek operation returns the top element from the stack without removing it.
A queue, on the other hand, is a data structure that follows the First In First Out (FIFO) principle, meaning that the first element added to the queue is the first one to be removed. It can be implemented using an array or a linked list. The basic operations that can be performed on a queue include enqueueing, dequeue, and peeking. Enqueue operation adds an element to the end of the queue, the dequeue operation removes the front element from the queue, and the peek operation returns the front element from the queue without removing it.
In summary, the main difference between a stack and a queue is the order in which elements are removed. A stack follows the LIFO principle while a queue follows the FIFO principle.
- What is the difference between a shallow copy and a deep copy?
In C++, a shallow copy of an object copies the reference to the object, rather than creating a new object with a new memory address. A deep copy, on the other hand, creates a new object with a new memory address and copies the contents of the original object to the new object.
For example, if you have a class MyClass and create an object obj1 of that class, a shallow copy of obj1 would only create a new reference to the same object in memory, while a deep copy would create a new object with a new memory address and copy all the member variables of obj1 to the new object.
A shallow copy can be done by default copy constructor and assignment operator and a deep copy is done by writing a custom copy constructor and assignment operator.
- How do you implement a linked list in C++?
A linked list is a data structure that consists of a sequence of elements called nodes, where each node contains a reference to the next element in the list. To implement a linked list in C++, you can create a class or struct that represents a node and contains a reference to the next node in the list, as well as any data you want to store in the node. Here is an example of a simple implementation of a singly linked list in C++:
class Node {
public:
int data;
Node* next;
Node(int data) {
this->data = data;
next = nullptr;
}
};
class LinkedList {
private:
Node* head;
public:
LinkedList() {
head = nullptr;
}
void addToFront(int data) {
Node* newNode = new Node(data);
newNode->next = head;
head = newNode;
}
void removeFromFront() {
if (head != nullptr) {
Node* temp = head;
head = head->next;
delete temp;
}
}
void printList() {
Node* temp = head;
while (temp != nullptr) {
cout << temp->data << " ";
temp = temp->next;
}
cout << endl;
}
};
- Can you explain the concept of exception handling in C++?
Exception handling is a mechanism in C++ that allows you to handle unexpected events or errors that occur during the execution of your program. When an exception is thrown, the program will transfer control to a specific block of code known as an exception handler, where the exception can be handled and the program can continue executing.
The try-catch statement is used to handle exceptions in C++. The try block contains the code that might throw an exception, and the catch block contains the code that will be executed if an exception is thrown. Here is an example of how to use the try-catch statement:
try {
int x = 5;
int y = 0;
int z = x / y;
} catch (const exception& e) {
cout << "An exception occurred: " << e.what() << endl;
}
- What is the difference between a vector and an array?
An array is a fixed-size collection of elements of the same data type, while a vector is a dynamic array that can grow or shrink as needed. In C++, arrays are defined with a fixed size at compile time, whereas vectors can be resized at runtime. Also, vectors provide more functionality than arrays, for example, vectors provide a number of member functions for adding, removing, and manipulating elements, whereas arrays do not have such functionality.
- What is the difference between a function and a method?
A function is a standalone block of code that performs a specific task, while a method is a function that is associated with a class or object. In C++, functions are declared outside of any class or struct, while methods are declared inside a class or struct. Also, methods can access and modify the member variables of the class or object they are associated with, while functions cannot.
- How do you implement a hash table in?
A hash table is a data structure that stores key-value pairs and uses a hash function to map the key to an index in an array. To implement a hash table in C++, you can create a class or struct that contains an array of linked lists (or another data structure) to store the key-value pairs and a hash function to map the keys to array indices.
The hash function takes a key as input and returns an index in the array where the key-value pair should be stored. Here is an example of a simple hash table implementation in C++:
class HashTable {
private:
vector<list<pair<int, int>>> table;
int size;
int hashFunction(int key) {
return key % size;
}
public:
HashTable(int size) {
this->size = size;
table.resize(size);
}
void insert(int key, int value) {
int index = hashFunction(key);
table[index].push_back({ key, value });
}
int search(int key) {
int index = hashFunction(key);
for (auto const& [k, v] : table[index]) {
if (k == key) {
return v;
}
}
return -1;
}
};
- Can you explain the concept of memory management?
Memory management in C++ refers to the process of allocating, deallocating, and managing memory during the execution of a program. In C++, memory management is typically done using the new and delete operators, which are used to allocate and deallocate memory dynamically.
When a block of memory is allocated using new, the program is responsible for deallocating that memory using delete when it is no longer needed. Failure to properly manage memory can lead to a variety of issues, such as memory leaks and buffer overflow.
- What is the difference between a static and a dynamic library?
A static library is a collection of object files that are combined into a single file at compile-time, while a dynamic library is a separate file that is loaded and linked to a program at runtime. Static libraries are linked to the program at compile-time, thus their code becomes part of the executable, whereas dynamic libraries are loaded at runtime and thus their code resides outside of the executable.
This means that static libraries increase the size of the executable, whereas dynamic libraries do not. Also, dynamic libraries can be shared among multiple programs, whereas static libraries cannot.
- What is the difference between pass-by-value and pass-by-reference?
In C++, when a variable is passed by value, a copy of the variable is created and passed to the function, whereas when a variable is passed by reference, a reference to the original variable is passed to the function.
When a variable is passed by value, any changes made to the variable within the function will not affect the original variable, whereas when a variable is passed by reference, any changes made to the variable within the function will be reflected in the original variable. To pass a variable by reference in C++, you use the & operator, like this:
void myFunction(int& x) {
x = x + 1;
}
- How do you implement a binary tree?
A binary tree is a data structure that consists of nodes, where each node contains a value and references to its left and right child nodes. To implement a binary tree in C++, you can create a class or struct that represents a node and contains a value, a left child pointer, and a right child pointer. Here is an example of a simple implementation of a binary tree in C++:
class Node {
public:
int data;
Node* left;
Node* right;
Node(int data) {
this->data = data;
left = right = nullptr;
}
};
class BinaryTree {
private:
Node* root;
public:
BinaryTree() {
root = nullptr;
}
void addNode(int data) {
root = addNode(root, data);
}
Node* addNode(Node* node, int data) {
if (node == nullptr) {
node = new Node(data);
} else if (data <= node->data) {
node->left = addNode(node->left, data);
} else {
node->right = addNode(node->right, data);
}
return node;
}
void printInOrder() {
printInOrder(root);
}
void printInOrder(Node* node) {
if (node == nullptr) {
return;
}
printInOrder(node->left);
cout << node->data << " ";
printInOrder(node->right);
}
};
In this example, the addNode function is a recursive function that is used to add a new node to the binary tree. The printInOrder function is also a recursive function that is used to print the values of the nodes in the binary tree in an in-order traversal.
This is a basic example of a Binary Tree and it can be implemented in different ways with different variations based on the need.
Conclusion
Preparing for a C++ interview requires a thorough understanding of the language and its features, as well as a solid understanding of common data structures and algorithms. It’s also important to have a good understanding of the underlying concepts of the language, including memory management and exception handling. Being familiar with the latest features and best practices in C++ will help you stand out as a candidate and excel in your interview.
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