How to implement custom sorting rules using C++ lambda expressions?

Use C Lambda expressions to customize sorting rules to flexibly define sorting logic. The syntax is: [capture list](parameters) -> return type { body }. In the actual case, the lambda expression sortLambda sorts by string length, and the output is: dog, apple, banana, cherry, elephant.

Use C Lambda expression to customize sorting rules

Lambda expression is an anonymous function that can be used in C to define custom sorting rules. It provides an easy and flexible way to sort your data based on custom logic.

Syntax

The typical lambda expression syntax is as follows:

[capture list](parameters) -> return type { body }

Among them:

• capture list : Optional, used to capture references to external variables.
• parameters: Optional, used to obtain input parameters.
• -> return type: Optional, used to specify the return type.
• body: Function body, containing the code to be executed.

Practical case

The following is a practical case using lambda expression to customize sorting rules, which is used to sort a string vector by its length:

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main() {
    vector<string> strings = {"apple", "banana", "cherry", "dog", "elephant"};

    // 定义 lambda 表达式，将字符串按长度排序
    auto sortLambda = [](const string& a, const string& b) { return a.length() < b.length(); };

    // 使用 lambda 表达式对向量排序
    sort(strings.begin(), strings.end(), sortLambda);

    // 打印排序后的向量
    for (const string& s : strings) {
        cout << s << endl;
    }

    return 0;
}

Output

dog
apple
banana
cherry
elephant

In this example, the lambda expression sortLambda captures the external variables a and ## A reference to #b, and returns whether the length of a is less than the length of b. The sort function sort uses this lambda expression to sort a vector of strings in ascending order of their length.

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