Shark-Toolz

In-depth exploration of C + + container principles to improve your programming skills

By shark-toolz

2024-12-03 18:37:13 49 Views
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In C + + programming, containers are a key concept for storing and managing data. They provide a flexible and efficient way to organize and manipulate data. This blog will delve into several major container types in C + + and how they work, including arrays, vectors, lists, mappings, and hash tables. We will describe the definitions, types of these containers, and how to use them effectively. In addition, the article will discuss how to optimize the performance of C + + containers, and provide some practical tips and suggestions to help you make better use of these containers in actual development. Whether you are a C + + novice or an experienced developer, this blog will provide you with valuable information and insights.
In C + + programming, containers are the basic tools for storing and managing data.

They provide an efficient and flexible way to organize and manipulate data collections.

This article will deeply discuss the basic principles, types and application scenarios of C + + containers to help readers improve their programming skills.

1. Overview of C + + Containers.

The C + + standard library provides a variety of containers, each with its own specific purpose and characteristics.

These containers are mainly divided into serial containers (such as arrays, vectors, lists, etc.) and relational containers (such as maps, collections, hash tables, etc.).

Knowing the definitions and types of these containers is critical to choosing the right container.

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1.1 Sequential containers.

Serial containers store elements in order, allowing access to elements by index.

Common serial containers include: - # Array (Array) #: Fixed-size contiguous memory blocks for scenarios that require fast random access.

- # Vector (Vector) #: Dynamic array, supports fast random access and dynamic expansion.

- # List (List) #: Doubly linked list, suitable for frequent insertion and deletion operations.

- # Double-ended queue (Deque) #: A sequence container with double-ended openings that supports efficient insertion and deletion operations at both ends.

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1.2 Associative containers.

The associative container stores elements through key-value pairs, providing efficient lookup functions.

Common relational containers include: - # Mapping (Map) #: Based on red-black tree implementation, key sorting storage, support for quick search, insertion and deletion operations.

- # Collection (Set) #: Based on a balanced binary tree, it stores unique elements and supports quick search, insertion and deletion operations.

- # Multimap (Multimap) #: Allows multiple elements with the same key to exist.

- # Multiset (Multiset) #: Allows multiple elements with the same value to exist.

- # Unordered Map #: Based on the hash table implementation, the order of the elements is not guaranteed.

- # Unordered Set #: Based on the hash table implementation, the order of the elements is not guaranteed.

2. Detailed explanation of common C + + containers.

Below we introduce several commonly used C + + containers in detail, and explain their working principles and application scenarios.

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2.1 vector (Vector).

A vector is a dynamic array that supports fast random access and dynamic expansion.

It internally uses contiguous memory space to store elements, so it is cache-friendly. 


#include 
#include 

int main() {
    std::vector vec = {1, 2, 3, 4, 5};
    vec.push_back(6); // 添加元素
    for (int i = 0; i < vec.size(); ++i) {
        std::cout << vec[i] << " "; // 输出元素
    }
    return 0;
}
\n#
2.2 List (List).

A list is a doubly linked list suitable for frequent insertion and deletion operations.

It does not support random access, but can be efficiently traversed by iterators. 


#include 
#include 

int main() {
    std::list lst = {1, 2, 3, 4, 5};
    lst.push_back(6); // 添加元素
    for (auto it = lst.begin(); it != lst.end(); ++it) {
        std::cout << *it << " "; // 输出元素
    }
    return 0;
}
\n#
2.3 Mapping (Map).

A mapping is an associative container based on a red-black tree that stores key-value pairs and presses them for sorting.

It supports efficient find, insert and delete operations. 


#include 
#include 

int main() {
    std::map map;
    map[1] = "one";
    map[2] = "two";
    map[3] = "three";
    for (const auto& pair : map) {
        std::cout << pair.first << ": " << pair.second << "\n"; // 输出键值对
    }
    return 0;
}
3. Tips for optimizing the performance of C + + containers.

In actual development, choosing the right container and optimizing its performance is critical to improving program efficiency.

Here are some optimization tips: - # Pre-allocated memory #: For containers such as vectors and strings, pre-allocating enough memory can reduce the number of memory reallocations, thereby improving performance.

- # Avoid unnecessary copying #: Use references or pointers to pass large objects, reducing the overhead of copying operations.

- # Choose the right container #: Choose the right container type according to your specific needs.

For example, if you need to find elements frequently, you can choose a map or a collection; if you need to insert and delete elements frequently, you can choose a list or a double-ended queue.

- # Use move semantics #: C + + 11 introduces move semantics, through rvalue references and std::moveResources can be transferred effectively and unnecessary copying can be avoided.

4. Practical application cases.

In order to better understand the application of C + + containers, let's look at a practical case: implementing a simple student performance management system. 


#include 
#include 
#include 
#include 

class Student {
public:
    std::string name;
    int id;
    std::map grades; // 课程名 -> 成绩
};

class GradeManager {
private:
    std::vector students;
public:
    void addStudent(const Student& student) {
        students.push_back(student);
    }
    
    void addGrade(int studentId, const std::string& course, int grade) {
        for (auto& student : students) {
            if (student.id == studentId) {
                student.grades[course] = grade;
                break;
            }
        }
    }
    
    void printGrades(int studentId) const {
        for (const auto& student : students) {
            if (student.id == studentId) {
                std::cout << "Grades for " << student.name << ":\n";
                for (const auto& pair : student.grades) {
                    std::cout << pair.first << ": " << pair.second << "\n";
                }
                break;
            }
        }
    }
};

int main() {
    GradeManager gm;
    Student alice = {"Alice", 1, {}};
    Student bob = {"Bob", 2, {}};
    gm.addStudent(alice);
    gm.addStudent(bob);
    gm.addGrade(1, "Math", 90);
    gm.addGrade(1, "Science", 85);
    gm.addGrade(2, "Math", 78);
    gm.printGrades(1); // 输出Alice的成绩
    gm.printGrades(2); // 输出Bob的成绩
    return 0;
}
In this case, we used vectors to store student information and mappings to store each student's course grades.

This combination allows us to efficiently manage and query student grade information.

Conclusion.

C + + containers are an integral part of C + + programming. They provide rich data structures and algorithms to help us manage and manipulate data efficiently.

Through in-depth understanding of the principles and application scenarios of various containers, combined with optimization skills, we can write more efficient and stronger programs.

I hope this article can help you better understand and apply C + + containers and improve your programming skills.

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