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C++ can be described as a better version of the C programming language. The cross-platform language with a general purpose can help programmers gain increased control over system memory and resources. Knowing how to answer the most common C++ interview questions is the best way to show employers that you are the right fit for the job. Dive deeper to learn about the most common CPP interview questions and how to answer them.
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C++ interview can be very difficult to get into, so it's important to know what you're getting into. We bring to you the top C++ Interview Questions asked with sample answers that would help demonstrate your knowledge of the industry and the job role.
Some of the most basic C++ interview questions are as follows:
Object-oriented programming is data-focused, with an object as the primary programming unit. C++ can enable OOP with the help of different classes.
It is one of the C++ interview questions that you must be able to answer to impress the interviewer. A few key differences between the two programming languages are as follows:
C | C++ |
---|---|
Procedure-oriented | Object-oriented |
Does not facilitate data hiding | Enables data hiding |
Subset of C++ | Superset of C |
Lacks function and operator overloading | Allows function and operator overloading |
Functions are not definable within structures. | Functions are definable within structures. |
It is one of the C++ interview questions and answers that interviewers expect all candidates to know. A few key features of the C++ programming language are as follows:
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It is one of the easiest CPP interview questions for beginners. Inheritance refers to extending and reusing existing classes without altering them. As a result, hierarchical relationships get established between them. Inheritance is somewhat similar to embedding objects within classes.
Polymorphism in C++ makes a particular object or function act differently in multiple scenarios. In simple terms, it revolves around conveying the same message in different ways. For instance, the "+" operator is useful for performing different functions in different scenarios.
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Overloading refers to multiple functions having the same name with different parameters. Overriding in C++ involves redefining a function with the same name and signature as the inheriting class.
Access specifiers in the C++ programming language are leveraged to define the way of accessing different attributes and methods of a class. You will find three types of access specifiers in C++:
It is one of the most frequently asked C++ interview questions to freshers. A class is a user-defined data structure with a keyword class containing functions and data similar to its members. Objects are data structures that can be defined as class instances.
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It is one of the trickiest CPP interview questions. A structure in C++ is quite similar to a class except for a handful of differences. A few differences between struct and class are as follows:
Struct | Class |
---|---|
Struct members are public by default. | Class members are private by default. |
While deriving a struct from a struct or class, the default access specifiers will be public. | While serving a class, the default access specifiers remain private. |
Read: Advantages and Disadvantages of Arrays in C, C++, and Java
Let’s move to the c++ interview questions for intermediate.
A few CPP interview questions for the intermediate level are as follows:
A C++ shallow copy will store a copy of the original object while finally copying only the reference address. A deep copy will store a copy of the original object along with repetitive copies.
Function templates in C++ can be described as special functions operating with generic types. The functionality of these templates can be adapted to more than one class without having to repeat the whole code. In C++, this process is achieved with the help of template parameters.
You should be using the class template for creating a class parameterized by any particular type. A function template is for creating a function operating on different types.
Function templates are capable of performing type deduction. They can be employed to develop factory functions:
//Deduces the types of T1 and T2, so //for example, a pair<int, double> can be created //by `make_pair(10, 1.2)` template pair<T1, T2> make_pair(T1&& t1, T2&& t2) { return {std::forward(t1), std::forward(t2)}; }
Class templates are utilized to code programs executed at the time of compilation. Class templates are executed using types like values and template instantiations with patterns aligning as pure functions. One example of this is the class template set removing const from a type:
//Removes all `const` from a type, for example: //`remove_const_recursive::type` //is the type `int*volatile`. template struct remove_const_recursive { typedef T type; }; template struct remove_const_recursive { typedef typename remove_const_recursive::type volatile type; }; template struct remove_const_recursive { typedef typename remove_const_recursive::type volatile type; }; template struct remove_const_recursive { typedef typename remove_const_recursive::type type; }; template struct remove_const_recursive<T&> { typedef typename remove_const_recursive::type& type; }; template struct remove_const_recursive<T*> { typedef typename remove_const_recursive::type* type; };
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It is one of the most important C interview questions. Operator overloading can be defined as a polymorphism for compilation time. This technique can help assign a special meaning to any existing operator without modifying its real meaning.
In the C++ programming language, operators are used for user-defined classes. Therefore, C++ can assign a special meaning to operators for a specific data type. This ability can be titled operator overloading.
For instance, you can overload an operator "+" in a String class. It will ensure that you can concatenate more than one string with the help of the + operator. Some other classes where arithmetic operators might be overloaded include complex numbers, big integers, and fractional numbers.
Example: // C++ Program to Demonstrate the // working/Logic behind Operator // Overloading class A { statements; }; int main() { A a1, a2, a3; a3 = a1 + a2; return 0; } In this example, the type class A has 3 variables called a1, a2, and a3. This example involves adding two objects, a1 and a2, which belong to the user-defined type. But it's not allowed because the addition operator + is only used for operating on in-built data types. But in this example, class A is user-defined, which will make the compiler generate an error. That's where the concept of operator overloading can be applied. If you want to make the + operators add two class objects, you will have to redefine it in a way that it can add two class objects. The concept of operator overloading can help with it. The primary purpose of operator overloading is to use operators alongside class objects or variables.
It is one of the C++ interview questions and answers to demonstrate your awareness regarding different functions. The difference between virtual functions and pure virtual functions are as follows:
Virtual Function | Pure Virtual Function |
---|---|
Belongs to a base class which can be redefined by derived class | Belong to a base class whose declaration is available in the base class and needs to be defined within a derived class to prevent it from becoming an abstract |
Not abstract classes | Becomes abstract |
Syntax: virtual<func_type><func_name>()
virtual() { // code } |
Syntax: virtual() = 0; |
Definition is available in base class | No definition is available in base class |
Can be instantiated | Cannot be instantiated |
Does not affect compilation | Prevents compilation error but the derived class becomes abstract |
May or may not redefine virtual function of the base class | Derived classes can redefine pure virtual functions of the base class otherwise the derived class becomes abstract |
C++11 makes the auto keyword a new type specifier. It serves as a placeholder to deduce a type from the initial variable expression. As auto type deduction gets enabled, you won't be required to mention a type during variable declaration. Instead, the compiler will deduce the type of an auto variable from its initializer expression. One example of the auto-type deduction is as follows:
auto x = 1; //x : int float* p; auto x = p; //x : float* auto* y = p; //y : float* double f(); auto x = f(); //x : double const auto& y = f(); //y : const double& class R; R* h(); auto* x = h(); //x : R* auto y = h(); //y : R* int& g(); auto x = g(); //x : int const auto& y = g(); //y : const int& auto* z = g(); //error, g() does not return a pointer type
The function objects in C++ are useful for implementing operators (). Function objects are primarily used in the C++ standard library as container sorting criteria in algorithms.
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The feature of multiple inheritance in C++ enables a class to inherit from multiple classes. The inherited class constructors are called in the same order as their inheritance.
The keyword mutable is utilized for modifying a specific data member of a const object. After declaring a function as const, the pointer passed to the function turns into const. When a mutable gets added to a variable, it can enable a const pointer to modify members.
Understand: Fibonacci series in C
Let’s move to the c++ interview questions for experienced.
A few C++ interview questions and answers for experienced professionals are as follows:
These rules are used for creating exception-safe codes with formalized rules about resource management. These rules are useful for determining the usage of default class members to systematically achieve goals.
Malloc() and new are useful for allocating dynamic memory in a heap. The malloc() operator is a valuable C library function, also applicable in C++. You should prefer new when you are required to call the constructor class.
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You will be able to compile a program without the main() function by using macros. The code for it is as follows:
// C++ program to demonstrate the // a program without main() #include #define fun main int fun(void) { printf("Herovired"); return 0; }
The move semantics and rvalue references in C++ can help avoid irrelevant copies while working with temporary objects. They don't copy the temporary, which disappears anyway. Therefore, the resources necessary for temporary objects can be used for other objects.
The parameterized constructor can accept arguments or parameters. It can be called explicitly by passing values in the arguments. These arguments enable object initialization during its creation. The parameterized constructor will feature the same name as that of the class and can be used to overload constructors. An example of the parameterized constructor is as follows:
// CPP program to demonstrate // parameterized constructors #include using namespace std; class GFG { private: int x, y; public: // Parameterized Constructor GFG(int x1, int y1) { x = x1; y = y1; } int getX() { return x; } int getY() { return y; } }; int main() { // Constructor called GFG G(10, 15); // Access values assigned by constructor cout << "G.x = " << G.getX() << ", G.y = " << G.getY(); return 0; } Output: G.x = 10, G.y = 15
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A virtual destructor in C++ is applied in the base class to prevent the derived class object from getting destroyed. An example of this is as follows:
#include using namespace std; class Base { public: Base() { cout<<"Base constructor is called"<<"n"; } ~Base() { cout<<"Base class object is destroyed"<<"n"; } }; class Derived:public Base { public: Derived() { cout<<"Derived class constructor is called"<<"n"; } ~Derived() { cout<<"Derived class object is destroyed"<<"n"; } }; int main() { Base* b= new Derived; delete b; return 0; } Output: Base constructor is called Derived class constructor is called Base class object is destroyed
Let’s move to the next c++ interview question.
#include #include using namespace std; int main() { vector vec_1; vec_push_back("sample code"); vec_push_back("change example"); for(vector ::iterator i=vec_begin();i!=vec_end();++i) cout<<*i; return 0; }
#include <bits/stdc++.h> using namespace std; int main() { vector vec{ 1,9,4,3,2,8,5,7}; sort(vec.begin(), vec.end()); for (auto x : v) cout << x << "" ""; return 0; }
Find out: What is Arrays in C, C++
In this guide we have discussed some of the most important and common C++ interview questions with answers. Once you are prepared with these C++ interview questions, you have a greater chance of getting the selected in the interview and crack the offer. When you are able to answer these questions, the interviewer will develop a certain level of trust in your skills. Therefore, keep expanding your C++ knowledge to impress employers and quality for high-paying jobs.
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Preparing for a C programming interview will increase your chances of getting hired. You will be able to develop a rough idea of the questions you can expect.
If you want to excel in a C interview, you should have a clear understanding of all the basic concepts. If you are unaware of any particular concept, you should show the employers that you are willing to learn that.
Some of the key areas that you should focus on for your C++ interviews include data types, tokens, classes, objects, structure, and more. Remember that the level of the CPP interview questions will depend on your expertise in the field.
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