Real interview questions from top companies for C++. Includes theoretical concepts and coding problems.
What are the key features of C++?
C++ is a high-performance, compiled, general-purpose programming language that supports object-oriented, imperative, and functional programming paradigms. Its key features include templates, operator overloading, and smart pointers.
What is the difference between C and C++?
C is a procedural programming language, while C++ is an object-oriented programming language that builds upon C. C++ adds features such as classes, inheritance, polymorphism, and templates, making it a more powerful and flexible language.
What is a pointer in C++?
A pointer in C++ is a variable that stores the memory address of another variable. Pointers are used to indirectly access and manipulate the values stored in memory locations.
What is the purpose of the 'new' and 'delete' operators in C++?
The 'new' operator is used to dynamically allocate memory for objects, while the 'delete' operator is used to deallocate memory that was previously allocated using 'new'. This helps to prevent memory leaks and ensures proper memory management.
What is a class in C++?
A class in C++ is a user-defined data type that encapsulates data and functions that operate on that data. Classes are the foundation of object-oriented programming in C++ and are used to create objects that can interact with each other.
What is inheritance in C++?
Inheritance in C++ is a mechanism that allows one class to inherit the properties and behavior of another class. The inheriting class is called the derived class, and the class being inherited from is called the base class.
What is polymorphism in C++?
Polymorphism in C++ is the ability of an object to take on multiple forms, depending on the context in which it is used. This can be achieved through function overloading, function overriding, or operator overloading.
What is a template in C++?
A template in C++ is a feature that allows functions and classes to operate on generic types, rather than being limited to a specific type. Templates enable code reuse and generic programming.
What is the difference between a reference and a pointer in C++?
A reference in C++ is an alias for an existing variable, while a pointer is a variable that stores the memory address of another variable. References are safer and more convenient to use than pointers, but they have limited functionality.
What is a smart pointer in C++?
A smart pointer in C++ is a class that provides automatic memory management for dynamically allocated objects. Smart pointers, such as unique_ptr and shared_ptr, help to prevent memory leaks and dangling pointers.
What is the purpose of the 'const' keyword in C++?
The 'const' keyword in C++ is used to declare variables that cannot be modified once they are initialized. This helps to ensure data integrity and prevent unintended changes to variables.
What is a lambda function in C++?
A lambda function in C++ is a small, anonymous function that can be defined inline within a larger expression. Lambda functions are useful for creating short, one-time-use functions.
What is a functor in C++?
A functor in C++ is a class that overloads the function call operator, allowing objects of the class to be used as functions. Functors are useful for creating function objects that can be used with algorithms and containers.
What is the difference between a vector and a list in C++?
A vector in C++ is a dynamic array that provides random access to its elements, while a list is a doubly-linked list that provides sequential access to its elements. Vectors are generally faster and more efficient than lists, but lists are more flexible and suitable for certain types of operations.
What is a map in C++?
A map in C++ is a container that stores key-value pairs, allowing for efficient lookup and retrieval of values based on their corresponding keys. Maps are implemented as balanced binary search trees, providing fast search, insertion, and deletion operations.
What is a set in C++?
A set in C++ is a container that stores unique elements, providing fast lookup and insertion operations. Sets are implemented as balanced binary search trees, ensuring efficient search, insertion, and deletion operations.
What is the purpose of the 'std::move' function in C++?
The 'std::move' function in C++ is used to transfer ownership of an object, allowing for efficient transfer of resources without unnecessary copying. This helps to improve performance and reduce memory usage.
What is the difference between a copy constructor and a move constructor in C++?
A copy constructor in C++ is a special constructor that creates a copy of an existing object, while a move constructor is a special constructor that transfers ownership of an object, allowing for efficient transfer of resources without unnecessary copying.
Write a C++ function to reverse a linked list.
structNode {
int data;
Node* next;
}
;
voidreverseList(Node** head){
Node* prev = NULL;
Node* current = *head;
Node* next = NULL;
while (current != NULL) {
next = current->next;
current->next = prev;
prev = current;
current = next;
}
*head = prev;
}
Write a C++ function to find the maximum element in an array.
intfindMax(int arr[], int n) {
int max = arr[0];
for (int i = 1;
i < n;
i++) {
if (arr[i] > max) {
max = arr[i];
}
}
return max;
}
Write a C++ function to implement binary search.
intbinarySearch(int arr[], int n, int target) {
int left = 0;
int right = n - 1;
while (left <= right) {
int mid = left + (right - left) / 2;
if (arr[mid] == target) {
return mid;
}
elseif (arr[mid] < target) {
left = mid + 1;
}
else {
right = mid - 1;
}
}
return-1;
}
Write a C++ function to find the first duplicate in an array.
intfindFirstDuplicate(int arr[], int n){
std::unordered_set<int> seen;
for (int i = 0;
i < n;
i++) {
if (seen.find(arr[i]) != seen.end()) {
return arr[i];
}
seen.insert(arr[i]);
}
return-1;
}
Write a C++ function to implement merge sort.
voidmergeSort(int arr[], int n) {
if (n <= 1) {
return;
}
int mid = n / 2;
int left[mid];
int right[n - mid];
for (int i = 0;
i < mid;
i++) {
left[i] = arr[i];
}
for (int i = mid;
i < n;
i++) {
right[i - mid] = arr[i];
}
mergeSort(left, mid);
mergeSort(right, n - mid);
merge(left, right, arr, mid, n - mid);
}
voidmerge(int left[], int right[], int arr[], int n, int m) {
int i = 0;
int j = 0;
int k = 0;
while (i < n && j < m) {
if (left[i] <= right[j]) {
arr[k] = left[i];
i++;
}
else {
arr[k] = right[j];
j++;
}
k++;
}
while (i < n) {
arr[k] = left[i];
i++;
k++;
}
while (j < m) {
arr[k] = right[j];
j++;
k++;
}
}
Write a C++ function to find the minimum window substring that contains all characters of a given string.
std::string minWindow(std::string s, std::string t){
if (s.length() < t.length()) {
return"";
}
std::unordered_map<char, int> tCount;
for (char c : t) {
tCount[c]++;
}
int required = tCount.size();
int left = 0;
int minLen = INT_MAX;
std::string minWindow = "";
std::unordered_map<char, int> windowCounts;
for (int right = 0;
right < s.length();
right++) {
char c = s[right];
if (tCount.find(c) != tCount.end()) {
windowCounts[c]++;
if (windowCounts[c] == tCount[c]) {
required--;
}
}
while (required == 0) {
if (right - left + 1 < minLen) {
minLen = right - left + 1;
minWindow = s.substr(left, right - left + 1);
}
char c = s[left];
if (tCount.find(c) != tCount.end()) {
if (windowCounts[c] == tCount[c]) {
required++;
}
windowCounts[c]--;
}
left++;
}
}
return minWindow;
}
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