The C standard library helps developers improve code quality by providing efficient tools. 1. STL containers should be selected according to the scene, such as vector suitable for continuous storage, list suitable for frequent insertion and deletion, and unordered_map is suitable for fast search; 2. Standard library algorithms such as sort, find, and transform can improve efficiency and reduce errors; 3. Intelligent pointers unique_ptr and shared_ptr effectively manage memory to avoid leakage; 4. Other tools such as optional, variant, and function enhance code security and expressiveness. Mastering these core functions can significantly optimize development efficiency and code quality.

The C standard library is a core set of tools that every C developer needs to be familiar with. It not only provides basic data structures and algorithms, but also hides many practical but easily overlooked details. If you have written some C code, you may find that many problems can actually be solved through the existing functions of the standard library, but you may not have realized it yet.

1. STL container: It is important to choose the right type

STL (Standard Template Library) contains a series of commonly used container classes, such as vector , map , set , etc. They each have applicable scenarios, and choosing the right one can significantly improve performance and readability.

• vector is suitable for storing data continuously, with high access efficiency, but insertion and deletion are slower in the middle.
• list is suitable for frequent insertion and deletion operations, but the random access efficiency is poor.
• If you need a quick lookup, unordered_map is usually faster than map because it is implemented based on a hash table.

A common misunderstanding is to use vector no matter what the situation is. In fact, when you need to frequently query keywords, it is more appropriate to use map or unordered_map .

Also, pay attention to the memory management strategy of the container. For example, vector will reallocate memory and copy original elements when expanding capacity, which needs to be paid attention to in performance-sensitive scenarios.

2. Algorithms and iterators: Don't make your own wheels

The standard library has a rich variety of algorithms, from sorting to searching to transformations, covering almost all operations common in daily development. for example:

• std::sort() can sort containers
• std::find() is used to find out whether an element exists
• std::transform() can generate new data without changing the original data

When using these algorithms, most of the logic processing can be accomplished with iterators. And these algorithms are optimized and are usually more efficient and safer than the loops you write yourself.

For example, if you want to multiply all elements in a vector by 2, you can write this:

 std::vector<int> data = {1, 2, 3, 4};
std::transform(data.begin(), data.end(), data.begin(), [](int x) { return x * 2; });

This is much clearer than a manual write loop and is less prone to errors.

3. Smart pointer: Make memory management safer

The use of bare pointers in early C could easily lead to memory leaks, while modern C introduced smart pointers such as unique_ptr and shared_ptr , which greatly reduced such problems.

• unique_ptr means exclusive ownership, cannot be copied, can only be moved
• shared_ptr allows multiple pointers to share the same object, and automatically release resources through reference counting internally.

It is recommended to avoid using original pointers unless there are special needs. Especially in complex object life cycle management, smart pointers are almost a must.

However, pay attention to the problem of circular references: if two shared_ptr hold each other, the memory will never be released. At this time, you can use weak_ptr to break the loop.

4. Other utility tools: Don't ignore small but beautiful features

In addition to containers and algorithms, the standard library also has some lightweight but very useful components:

• std::optional : Used to express a value that may not exist, which is safer than returning a null pointer
• std::variant : Similar to union, but can save multiple types of values
• std::function and lambda expressions: simplify the use of callback functions

For example, if you want to write a function that returns a possible failure, you can use std::optional :

 std::optional<int> findValue(const std::vector<int>& data, int target) {
    auto it = std::find(data.begin(), data.end(), target);
    if (it != data.end()) {
        return *it;
    }
    return std::nullopt;
}

Such interface semantics are clearer, and it is not easy for the caller to forget to judge whether it is valid.

Basically that's it. The C standard library has huge content, but mastering the commonly used parts can allow you to write more concise, safe and efficient code. Some features seem simple, but they can indeed solve a lot of trouble in actual projects.

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