When working with sorting algorithms in C++, you may encounter situations where you need to sort elements based on specific criteria or custom rules. In some cases, the default sorting order may not be suitable for your needs. Thankfully, C++ provides a way to define your own sorting literals to achieve custom sorting.

The std::sort Algorithm

Before diving into custom sorting literals, let’s first understand how the std::sort algorithm works in C++. The std::sort algorithm is part of the Standard Template Library (STL) and is widely used to sort elements in a container.

Here’s an example of using std::sort to sort a vector of integers in ascending order:

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

int main() {
    std::vector<int> numbers { 5, 2, 8, 1, 9 };

    std::sort(numbers.begin(), numbers.end());

    for (const auto& number : numbers) {
        std::cout << number << " ";
    }
    std::cout << std::endl;

    return 0;
}

The output of the above code will be: 1 2 5 8 9.

By default, std::sort uses the < operator to compare elements and determine their order. However, we can customize this behavior using custom sorting literals.

Custom Sorting Literals

A sorting literal is a function or a function object that defines the desired order of elements during sorting. To use custom sorting literals, we need to provide a comparison function that takes two elements as arguments and returns true if the first element should be placed before the second element; otherwise, it returns false.

Let’s consider a scenario where we want to sort a collection of strings based on their lengths in descending order. We can define a custom sorting literal to achieve this:

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

bool compareLengthDescending(const std::string& a, const std::string& b) {
    return a.length() > b.length();
}

int main() {
    std::vector<std::string> words { "apple", "banana", "cherry", "date" };

    std::sort(words.begin(), words.end(), compareLengthDescending);

    for (const auto& word : words) {
        std::cout << word << " ";
    }
    std::cout << std::endl;

    return 0;
}

The output of the above code will be: banana cherry apple date.

In this example, we define the compareLengthDescending function, which compares the lengths of two strings. The function returns true if the length of the first string is greater than the length of the second string, indicating that the first string should come before the second string in the sorted order.

By passing compareLengthDescending as the third argument to std::sort, we instruct the sorting algorithm to use our custom sorting literal for comparison.

Conclusion

Custom sorting literals in C++ provide a powerful way to define the desired order of elements during sorting based on specific criteria. By supplying a custom comparison function, you can sort elements in a container according to your requirements. This flexibility allows you to handle various sorting scenarios efficiently.

It’s important to note that using custom sorting literals incurs additional function call overhead during sorting, so be mindful of performance considerations when working with large data sets.

[#cplusplus #sorting #customliterals]