<p>The most common method of sorting vectors in C is to use the std::sort function. 1. First include the <algorithm> header file; 2. Call std::sort and pass in the vector's start and end iterator to achieve ascending sorting; 3. If you need to customize the sorting rules, such as descending or sorting by specific logic, pass in the comparison function or lambda expression through the third parameter; 4. When sorting structures or class objects, you can specify the sorting basis by overloading the to simplify the comparison logic. std::sort is flexible and efficient, but requires that the comparison function must meet "strict weak order", otherwise it may lead to undefined behavior. </algorithm></p> <p><img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175199945294692.jpg" class="lazy" alt="How to sort a vector in C?"></p> <p> The most common method to sort a <code>vector</code> in C is to use the <code>std::sort</code> function in the standard library. It is efficient and flexible, and is suitable for various types of <code>vector</code> , as long as the element type supports comparison operations. </p> <img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175199945326306.jpeg" class="lazy" alt="How to sort a vector in C?"><h3 id="Use-std-sort-to-sort-vector"> Use std::sort to sort vector</h3> <p> To sort a <code>vector</code> , you first need to include the <code><algorithm></algorithm></code> header file, then call <code>std::sort</code> and pass in <code>vector</code> 's start and end iterator. </p> <img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175199945476287.jpeg" class="lazy" alt="How to sort a vector in C?"><p> For example:</p><pre class='brush:php;toolbar:false;'> #include <iostream> #include <vector> #include <algorithm> int main() { std::vector<int> nums = {5, 2, 9, 1, 3}; std::sort(nums.begin(), nums.end()); for (int num : nums) { std::cout << num << " "; } }</pre><p> This code will output: <code>1 2 3 5 9</code> . </p><img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175199945658801.jpeg" class="lazy" alt="How to sort a vector in C?" /><p> By default, <code>std::sort</code> is arranged in ascending order. If you want to sort in descending order or have other sorting rules, you need to customize the comparison function.</p><h3 id="Custom-sorting-rules"> Custom sorting rules</h3><p> If you want to sort <code>vector</code> according to custom rules, such as from large to small, you can pass a comparison function or lambda expression in the third parameter of <code>std::sort</code> .</p><p> Take an example of descending order:</p><pre class='brush:php;toolbar:false;'> std::sort(nums.begin(), nums.end(), [](int a, int b) { return a > b; });</pre><p> You can also encapsulate the comparison logic into a function object or a normal function, suitable for more complex sorting logic.</p><p> Common scenarios include:</p><ul><li> Sort by string length <code>vector<string></code></li><li> Sort by a field in the structure</li><li> Custom sorting floating point numbers (such as ignoring accuracy differences)</li></ul><p> Note: Comparison functions must satisfy "strict weak ordering", otherwise undefined behavior may result.</p><h3 id="Sort-structure-or-class-objects"> Sort structure or class objects</h3><p> When the object you want to sort is a structure or class, you can overload the <code><</code> operator or provide a custom comparison function to implement sorting.</p><p> For example, there is a structure that represents students:</p><pre class='brush:php;toolbar:false;'> struct Student { std::string name; int age; }; bool compare_by_age(const Student& a, const Student& b) { return a.age < b.age; } std::vector<Student> students = {{"Alice", 20}, {"Bob", 18}, {"Charlie", 22}}; std::sort(students.begin(), students.end(), compare_by_age);</pre><p> The above code will sort students in ascending order by age. If you want to sort by name, just modify the comparison function.</p> <p> In addition, C 20 introduces <code>operator</code> (three-way comparison operator), which can simplify the comparison logic between structures, but not all projects enable C 20.</p> <h3 id="Basically-that-s-it"> Basically that's it</h3> <p> In general, using <code>std::sort</code> sorting <code>vector</code> is very simple, the key is to master how to pass in the appropriate comparison method. For basic data types, default sorting is enough; for complex types, custom comparison functions or lambdas come in handy.</p> <p> It is not complicated, but it is easy to ignore whether the writing method of the comparison function complies with the specification, especially whether the return value is consistent and stable, otherwise it may lead to sorting errors or program crashes.</p>

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