Custom sorting literals in C++

23 Oct 2023

customsort

Sorting a collection of elements is a common task in programming. The C++ standard library provides various sorting algorithms such as std::sort to sort elements in ascending order. By default, the sorting is performed based on the built-in comparison operators < and >.

However, there may be cases where you need to sort elements in a custom order that is not defined by the default comparison operators. In such situations, you can use custom sorting literals in C++ to define your own comparison criteria.

Using Custom Sorting Literals

To use custom sorting literals, you need to define your own comparison function, functor, or lambda expression. These can be passed as an argument to the sorting algorithm.

Let’s consider an example where we want to sort a vector of strings based on the length of the strings. We can define a lambda expression that compares the length of two strings:

std::vector<std::string> strings = { "apple", "banana", "cherry", "date" };

std::sort(strings.begin(), strings.end(), [](const std::string& a, const std::string& b){
    return a.length() < b.length();
});

In this example, the lambda expression [](const std::string& a, const std::string& b){ return a.length() < b.length(); } acts as a custom sorting literal. It specifies that the strings should be sorted based on their length.

Custom Sorting Literals with Function Objects

Alternatively, you can define a custom sorting literal using a function object. Function objects are objects that behave like functions by overloading the operator() function.

Here’s an example of using a function object for custom sorting:

struct LengthComparator {
    bool operator()(const std::string& a, const std::string& b) const {
        return a.length() < b.length();
    }
};

std::vector<std::string> strings = { "apple", "banana", "cherry", "date" };

std::sort(strings.begin(), strings.end(), LengthComparator());

In this example, LengthComparator is a function object with the operator() overloaded. It compares the length of two strings, allowing us to sort the vector based on the length of the strings.

Conclusion

Custom sorting literals in C++ provide you with the flexibility to define custom sorting criteria for your elements. By using lambda expressions or function objects, you can craft your own comparison logic and sort your data accordingly.

Using these techniques, you can sort elements based on any custom criteria that you require, beyond the default comparison operators.

References:

#cpp #customsort