interview
c-new-features
C进阶

C++ 面向对象面试题, C++进阶

C++ 面向对象面试题, C++进阶

QA

Step 1

Q:: 什么是面向对象编程(OOP)？

A:: 面向对象编程是一种程序设计范式，通过使用类和对象来组织代码。OOP的核心概念包括封装、继承、多态和抽象。

Step 2

Q:: 解释C++中的封装（Encapsulation）。

A:: 封装是将数据和操作数据的方法结合在一起，隐藏对象的内部状态，并只通过公开的方法与对象进行交互。这可以通过使用访问修饰符（如public、protected、private）来实现。

Step 3

Q:: 什么是继承（Inheritance）？在C++中如何实现？

A:: 继承是一种机制，允许一个类（子类）继承另一个类（基类）的属性和方法，从而实现代码的复用。C++中使用冒号符号（:）来指定继承。例如：class DerivedClass : public BaseClass {}。

Step 4

Q:: 什么是多态（Polymorphism）？C++中如何实现？

A:: 多态性允许一个函数或方法根据对象的类型来表现出不同的行为。C++中可以通过虚函数（virtual functions）来实现多态性。基类中的方法声明为virtual，子类可以覆盖（override）该方法。

Step 5

Q:: 解释C++中的抽象类（Abstract Class）和纯虚函数（Pure Virtual Function）。

A:: 抽象类是包含至少一个纯虚函数的类，不能直接实例化，只能作为基类使用。纯虚函数在声明时用=0表示，例如：virtual void functionName() = 0;。

用途

面试这些内容是因为面向对象编程是C`++`的重要组成部分，掌握OOP的概念和技术是开发健壮和可维护代码的基础。在实际生产环境中，OOP用于设计复杂系统时，有助于代码的重用、扩展性和可维护性。\n

相关问题

🦆
C++中的拷贝构造函数Copy Constructor是什么?▷

拷贝构造函数用于创建一个对象，该对象是通过使用另一个对象初始化的。其语法为：ClassName(const ClassName &obj);。

🦆
C++中的操作符重载Operator Overloading是什么?如何实现?▷

操作符重载允许用户定义或修改C++中的操作符的行为。可以通过在类中定义一个特殊的成员函数来实现。例如：ClassName operator+(const ClassName &obj);。

🦆
什么是RAIIResource Acquisition Is Initialization?在C++中如何实现?▷

RAII是一种管理资源的技术，其中资源的分配和释放绑定到对象的生命周期。在C++中，通过构造函数分配资源，通过析构函数释放资源。

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C++中的智能指针Smart Pointers是什么?它们有哪些类型?▷

智能指针是自动管理动态分配内存的对象，在不再使用时自动释放内存。常见的类型包括std::unique_ptr、std::shared_ptr和std::weak_ptr。

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C++11引入了哪些新的特性来增强面向对象编程?▷

C++11引入了许多新特性，包括右值引用（Rvalue References）、移动语义（Move Semantics）、智能指针（Smart Pointers）和lambda表达式（Lambda Expressions）等，这些特性提高了代码的性能和简洁性。

C++ STL面试题, C++进阶

QA

Step 1

Q:: 什么是C++ STL？

A:: STL(Standard Template Library)是C++标准模板库，是一组C++模板类和算法的集合。它包含四部分内容：算法、容器、迭代器和函数对象。STL通过泛型编程提高代码复用性和效率，提供了方便的操作数据结构的方法。

Step 2

Q:: STL中有哪些常用的容器？

A:: STL中常用的容器包括： 1. 顺序容器：vector、deque、list 2. 关联容器：set、multiset、map、multimap 3. 容器适配器：stack、queue、priority_queue

Step 3

Q:: vector与list的区别是什么？

A:: vector和list都是STL中的顺序容器，但它们有以下区别： 1. 底层实现：vector是基于动态数组实现的，list是基于双向链表实现的。 2. 访问速度：vector支持随机访问，访问时间复杂度为O(1)，list只支持顺序访问，访问时间复杂度为O(n)。 3. 插入和删除：在尾部插入和删除时，vector和list的时间复杂度都是O(1)，但在中间位置插入和删除时，vector的时间复杂度为O(n)，而list为O(1)。

Step 4

Q:: 如何在STL中使用迭代器？

A:: 迭代器是用于遍历容器的对象。STL提供五种迭代器：输入迭代器、输出迭代器、前向迭代器、双向迭代器和随机访问迭代器。以下是一个使用迭代器遍历vector的例子：

 
#include <iostream>
#include <vector>
using namespace std;
 
int main() {
    vector<int> v = {1, 2, 3, 4, 5};
    vector<int>::iterator it;
    for (it = v.begin(); it != v.end(); ++it) {
        cout << *it << ' ';
    }
    return 0;
}

Step 5

Q:: map和unordered_map的区别是什么？

A:: map和unordered_map都是STL中的关联容器，但它们有以下区别： 1. 底层实现：map是基于红黑树实现的，unordered_map是基于哈希表实现的。 2. 元素有序性：map中的元素是有序的，unordered_map中的元素是无序的。 3. 访问时间：map的查找、插入和删除操作的时间复杂度为O(log n)，unordered_map的查找、插入和删除操作的时间复杂度平均为O(1)。

用途

面试这些内容是为了考察候选人对C`++标准库及其使用方法的理解和掌握程度。STL是C++`编程的重要组成部分，了解和熟练使用STL能够极大地提高编程效率和代码质量。在实际生产环境中，开发者经常需要使用STL中的容器和算法来处理数据，进行高效的增删改查操作，以及实现复杂的数据处理任务。\n

相关问题

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如何使用STL中的sort算法?▷

STL中的sort算法用于对元素进行排序，默认使用升序排序。它的函数原型为：

 
template <class RandomIt>
void sort(RandomIt first, RandomIt last);

例子：

 
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
 
int main() {
    vector<int> v = {3, 1, 4, 1, 5, 9, 2, 6};
    sort(v.begin(), v.end());
    for (int n : v) {
        cout << n << ' ';
    }
    return 0;
}
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STL中如何使用自定义比较函数进行排序?▷

在sort算法中可以使用自定义比较函数进行排序。自定义比较函数需要实现一个二元谓词。例子：

 
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
 
bool compare(int a, int b) {
    return a > b; // 降序排序
}
 
int main() {
    vector<int> v = {3, 1, 4, 1, 5, 9, 2, 6};
    sort(v.begin(), v.end(), compare);
    for (int n : v) {
        cout << n << ' ';
    }
    return 0;
}
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什么是迭代器失效?如何避免?▷

迭代器失效指的是在迭代器操作期间，容器的结构发生改变，导致迭代器变得无效。常见的情况包括在vector或deque中插入或删除元素。避免迭代器失效的方法有： 1. 避免在迭代过程中修改容器。 2. 使用list等不易导致迭代器失效的容器。 3. 每次修改容器后重新获取迭代器。

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shared_ptr和unique_ptr有什么区别?▷

shared_ptr和unique_ptr都是C++11引入的智能指针，用于自动管理动态内存。区别如下： 1. 管理方式：shared_ptr允许多个指针共享同一对象的所有权，unique_ptr则独占对象的所有权。 2. 内存管理：shared_ptr使用引用计数管理内存，unique_ptr则在超出作用域时自动释放对象。 3. 使用场景：shared_ptr适用于需要共享所有权的场景，unique_ptr适用于明确单一所有权的场景。

🦆
如何在STL中使用Lambda表达式?▷

Lambda表达式是C++11引入的一种内联匿名函数，可以方便地在STL算法中使用。例子：

 
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
 
int main() {
    vector<int> v = {3, 1, 4, 1, 5, 9, 2, 6};
    sort(v.begin(), v.end(), [](int a, int b) { return a > b; }); // 降序排序
    for (int n : v) {
        cout << n << ' ';
    }
    return 0;
}

C++ 并发编程面试题, C++进阶

QA

Step 1

Q:: What is a race condition in C++ and how can it be avoided?

A:: A race condition occurs when multiple threads access and modify shared data concurrently without proper synchronization, leading to unpredictable results. It can be avoided by using synchronization mechanisms such as mutexes, locks, or atomic operations to ensure that only one thread can modify the shared data at a time.

Step 2

Q:: Explain the difference between a mutex and a spinlock in C++ concurrency.

A:: A mutex is a synchronization primitive that causes a thread to sleep while waiting for a lock, potentially allowing other threads to execute. A spinlock, on the other hand, continuously checks for the lock in a busy-wait loop, which can be more efficient in scenarios where the wait time is expected to be very short but can lead to CPU wastage if the wait is long.

Step 3

Q:: What is a deadlock, and how can you prevent it in C++?

A:: A deadlock occurs when two or more threads are waiting for each other to release locks, causing them to be stuck indefinitely. Deadlocks can be prevented by following strategies like lock ordering, where all threads acquire locks in a predefined order, or by using timeout mechanisms or lock-free data structures.

Step 4

Q:: How does the C++11 memory model support multi-threaded programming?

A:: The C++11 memory model provides a well-defined set of rules for the behavior of concurrent operations, including atomic operations, memory ordering, and synchronization. It allows developers to write portable and predictable multi-threaded code by specifying how memory operations can be reordered and how different threads interact with shared memory.

Step 5

Q:: What is the role of the std::atomic in C++?

A:: The std::atomic template in C++ is used to create atomic variables that support lock-free operations on shared data. These variables provide a safe way to perform read-modify-write operations without using mutexes, ensuring that no other thread can see intermediate states of the operation.

用途

Concurrency and parallelism are essential in modern software development`, particularly in environments where performance and scalability are critical, such as high-frequency trading, real-time systems, and large-scale web services. Understanding these concepts helps in writing efficient, safe, and predictable multi-threaded code, which is often required in performance-critical applications.`\n

相关问题

🦆
What is the difference between threading and parallelism?▷

Threading refers to the ability to run multiple threads concurrently within a single process, while parallelism involves executing multiple operations simultaneously across different cores or processors. Threading is often used for I/O-bound tasks, while parallelism is leveraged for CPU-bound tasks to improve performance.

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How do you handle thread safety when dealing with shared resources?▷

Thread safety can be handled by using synchronization primitives like mutexes, locks, and condition variables. Alternatively, using lock-free data structures or designing the system with immutability in mind can also help achieve thread safety without significant performance penalties.

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Explain the concept of false sharing and how to avoid it.▷

False sharing occurs when threads on different processors modify variables that reside on the same cache line, causing unnecessary invalidation and synchronization traffic. It can be avoided by padding shared data structures so that they occupy different cache lines or by restructuring the data layout to minimize cache line sharing.

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What is the purpose of the thread_local keyword in C++?▷

The thread_local keyword is used to declare variables that are unique to each thread, meaning each thread has its own separate instance of the variable. This is useful for storing data that is specific to the execution context of a thread, avoiding the need for synchronization.

🦆
How do you measure and improve the performance of concurrent code?▷

Performance of concurrent code can be measured using profiling tools to identify bottlenecks such as contention on shared resources, cache misses, and thread scheduling delays. Improvements can be made by optimizing synchronization, minimizing shared state, and maximizing parallelism by distributing workloads evenly across available threads.

C++ 新特性面试题, C++进阶

QA

Step 1

Q:: What are the main new features introduced in C++11?

A:: C++11 introduced several new features that enhanced the language's functionality and efficiency. Some key features include: auto keyword for type inference, range-based for loops, nullptr, lambda expressions, smart pointers, move semantics, rvalue references, constexpr, and the new threading support via std::thread. These features help improve code readability, reduce boilerplate code, and enable better resource management.

Step 2

Q:: What are lambda expressions in C++ and how do they work?

A:: Lambda expressions in C++ allow you to define anonymous functions inline. They can capture variables from their surrounding scope and can be used where function objects or function pointers are expected. A simple example is auto func = [](int a, int b) { return a + b; };``, which creates a lambda function that adds two integers. Lambda expressions are particularly useful for short, simple functions passed to algorithms like std::sort or std::for_each``.

Step 3

Q:: What is the significance of smart pointers in modern C++?

A:: Smart pointers, such as std::unique_ptr``, std::shared_ptr``, and std::weak_ptr``, are part of the C++ Standard Library introduced in C++11 to help manage dynamic memory more safely and efficiently. They automatically handle memory allocation and deallocation, reducing the chances of memory leaks and dangling pointers. For example, std::unique_ptr ensures that the memory it points to is only owned by one pointer at a time, making it ideal for exclusive ownership scenarios.

Step 4

Q:: Can you explain move semantics and how they differ from copy semantics in C++?

A:: Move semantics, introduced in C++11, allow the resources of a temporary object to be 'moved' rather than copied, optimizing performance by eliminating unnecessary deep copies. This is particularly useful in resource-intensive operations, such as transferring large data structures. Move semantics are implemented using rvalue references (e.g., T&&``) and move constructors/assignment operators. For instance, when returning large objects from a function, move semantics can significantly reduce overhead.

用途

These topics are essential in interviews because they cover fundamental advancements in C`++ that have shaped modern C++ programming. Understanding these features demonstrates a candidate's ability to write efficient, clean, and maintainable code. In production environments, these features are critical for optimizing performance, ensuring resource safety, and enhancing the overall code quality, especially in large-scale systems or applications requiring high efficiency, like real-time systems or performance-critical applications.`\n

相关问题

🦆
What are rvalue references, and how are they used in C++11?▷

Rvalue references (denoted by T&&``) allow a function to distinguish between an object that can be moved from (an rvalue) and one that cannot (an lvalue). They are primarily used in implementing move semantics. An example usage is in the move constructor, which transfers ownership of resources from a temporary object to a new one without deep copying.

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How does the auto keyword work in C++11 and later versions?▷

The auto keyword enables type inference, allowing the compiler to deduce the type of a variable at compile time. This is particularly useful for reducing redundancy and simplifying code, especially with complex types like iterators or lambda expressions. For example, auto it = v.begin(); automatically deduces the iterator type of v``.

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What is a nullptr, and how does it improve type safety compared to NULL?▷

nullptr is a keyword introduced in C++11 to represent a null pointer. It is type-safe and ensures that the pointer has no valid address. Unlike the traditional NULL``, which is typically defined as 0 or (void*)0``, nullptr has its own distinct type (``std::nullptr_t``), preventing unintended conversions.

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Explain the concept of constexpr in C++ and its benefits.▷

constexpr is a keyword introduced in C++11 that allows the evaluation of functions or expressions at compile time, if possible. This leads to optimizations by performing calculations during compilation rather than at runtime. It can be used to define constants, functions, and constructors. For example, constexpr int square(int x) { return x * x; } can be evaluated at compile time if x is known.

C++ 进阶面试题, C++进阶

QA

Step 1

Q:: 什么是C++中的RAII？

A:: RAII（Resource Acquisition Is Initialization）是一种C++中的资源管理惯用法，指在对象的生命周期内，资源的获取与释放被绑定在对象的构造和析构函数中。通过这种方式，可以确保在对象生命周期结束时自动释放资源，从而防止资源泄漏。这种方法广泛应用于内存管理、文件句柄管理、网络连接管理等场景。

Step 2

Q:: C++中的智能指针有哪些？

A:: C++中的智能指针包括std::unique_ptr、std::shared_ptr和std::weak_ptr。std::unique_ptr用于独占所有权的场景，确保资源不会被多个指针共享；std::shared_ptr用于共享所有权的场景，多个指针可以共同拥有资源，当最后一个std::shared_ptr被销毁时，资源会自动释放；std::weak_ptr用于解决std::shared_ptr循环引用的问题，它不增加资源的引用计数。

Step 3

Q:: 如何在C++中实现多态？

A:: C++中的多态性通常通过继承和虚函数来实现。基类定义一个或多个虚函数，并允许派生类重写这些函数。然后通过基类指针或引用调用这些虚函数时，实际调用的函数是在运行时根据指针或引用所指对象的类型决定的。这种机制称为动态绑定。

Step 4

Q:: C++中的虚函数表（Vtable）是什么？

A:: 虚函数表（Vtable）是一种由编译器生成的数据结构，用于支持C++的多态性。当一个类包含虚函数时，编译器会为这个类生成一个虚函数表，其中存储了虚函数的指针。对象在创建时会包含一个指向虚函数表的指针，这样通过基类指针或引用调用虚函数时，实际调用的函数是通过虚函数表动态解析的。

用途

面试这些内容的目的是为了评估候选人对C`++语言高级特性及其在实际开发中的应用的理解和掌握程度。在实际生产环境中，RAII和智能指针是资源管理的重要手段，可以有效防止内存泄漏和资源泄露问题；多态性是面向对象设计中不可或缺的概念，广泛用于设计灵活、可扩展的系统；虚函数表则是理解C++`运行时行为的关键，有助于优化代码性能并调试多态性相关问题。\n

相关问题

🦆
C++中的拷贝构造函数和赋值运算符的区别是什么?▷

拷贝构造函数用于创建一个新对象，并用一个已有对象初始化它；赋值运算符用于将一个已有对象的内容复制到另一个已经存在的对象中。编写这两个函数时需要注意深拷贝和浅拷贝的区别，以避免资源管理问题。

🦆
什么是C++中的左值和右值?▷

左值是指可以出现在赋值运算符左侧的表达式，代表一个内存位置；右值是指只能出现在赋值运算符右侧的表达式，通常代表一个临时值或常量。在C++11中，引入了右值引用（T&&）和std::move，用于实现高效的资源转移。

🦆
C++11中引入的关键字override和final有什么作用?▷

override用于显式声明一个派生类函数重写了基类的虚函数，以帮助编译器检查重写的正确性；final用于防止一个类被继承或者一个虚函数被进一步重写，确保类或函数的行为不会在继承链中被修改。

🦆
什么是C++中的多重继承?▷

多重继承是指一个类可以从多个基类继承，继承多个类的属性和方法。这种特性在C++中允许更复杂的类设计，但同时也引入了菱形继承问题和二义性问题，需要通过虚继承或明确指定调用路径来解决。

CC 中 jthread 和 thread 的区别