C++ Container Library Best Practices Guide

Best practice: Choose the right container: Choose the appropriate container according to the element access mode, such as vector, list, map. Capacity management: Pre-allocate container space (such as using reserve()) to improve insertion/deletion efficiency. Range accessors: Use begin()/end() to return an iterator for concise access to elements (such as a for loop). Practical case: For example, use a vector to store a large number of grades, pre-allocate space and use range accessor traversal to calculate the average grade.

C++ Container Library Best Practices Guide

Preface

C++ Container Library It is a powerful collection of data structures that can be used to efficiently manage and process data. However, improper use can lead to performance issues and code errors. This article provides guidance on C++ container library best practices to help you optimize your code and avoid common pitfalls.

Choose the right container

The container library provides various containers such as vectors, lists, and maps. It is important to choose the appropriate container based on data type and access pattern. The following are recommended containers for common situations:

• Frequently add or remove elements: Vector (vector)
• Need to find elements quickly: Map ( map) or unordered_map
• Need to preserve the insertion order of elements: List(list)
• Need to access the starting and ending points of elements: Double-ended queue (deque)

Capacity management

Allocating too little capacity will trigger frequent reallocation, resulting in poor performance . Pre-allocating enough capacity improves the efficiency of insert and delete operations. Use the reserve() method to reserve space for a vector, for example:

std::vector<int> vec;
vec.reserve(1000);

Range accessor

The range accessor provides a concise method to access the container element. Use the begin() and end() functions to return iterators, for example:

std::vector<int> vec = {1, 2, 3, 4, 5};
for (auto it = vec.begin(); it != vec.end(); ++it) {
  std::cout << *it << " ";
}

Practical case

Consider using The vector stores the scores of a large number of students. You can use reserve() to preallocate space and use range accessors to iterate over grades:

#include <vector>

int main() {
  std::vector<int> grades;
  grades.reserve(1000);

  // 添加成绩
  for (int i = 0; i < 1000; i++) {
    grades.push_back(rand() % 100);
  }

  // 计算平均成绩
  int sum = 0;
  for (auto grade : grades) {
    sum += grade;
  }
  double average = static_cast<double>(sum) / grades.size();

  std::cout << "平均成绩为：" << average << std::endl;

  return 0;
}

Conclusion

By following these best practices, you C++ container libraries can be used more efficiently. Choosing your containers wisely, managing capacity, and using range accessors can significantly improve the performance of your code, reduce errors, and enhance maintainability.

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