When working with data structures in C++, it is often necessary to sort elements in a specific order that may not be supported by the default comparison operators. In such cases, custom sorting literals can be used to define the desired order for sorting.

Using Custom Sorting Literals

To use custom sorting literals in C++, you can define a custom comparison function or a custom sorting class. The comparison function or class will dictate the order in which elements are sorted.

Custom Comparison Function

A custom comparison function allows you to define your own order for sorting elements. It takes two elements as input and returns a boolean value indicating whether the first element should come before the second element in the sorted sequence.

Here’s an example of a custom comparison function that sorts integers based on their absolute values:

bool compareIntegers(int a, int b) {
    return abs(a) < abs(b);
}

To use this custom comparison function for sorting, you can pass it as the third argument to the std::sort function from the <algorithm> header.

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

int main() {
    std::vector<int> numbers = {4, -2, 7, -5, 1};

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

    // Output: -2, 1, 4, -5, 7
    for (int num : numbers) {
        std::cout << num << " ";
    }

    return 0;
}

Custom Sorting Class

If you need more complex sorting logic or want to encapsulate the ordering criteria within a class, you can define a custom sorting class. The class should overload the function call operator operator(), which will be used for comparison during sorting.

Here’s an example of a custom sorting class that sorts strings based on their length:

class SortByLength {
public:
    bool operator()(const std::string& a, const std::string& b) const {
        return a.length() < b.length();
    }
};

To use this custom sorting class for sorting, you can create an instance of the class and pass it as the third argument to the std::sort function.

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

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

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

    // Output: date, apple, cherry, banana
    for (const std::string& word : words) {
        std::cout << word << " ";
    }

    return 0;
}

Conclusion

Custom sorting literals in C++ provide a flexible approach to define custom sorting criteria. Whether you need to sort based on complex rules or unconventional patterns, using custom comparison functions or sorting classes allows you to achieve the desired sorting order. By taking advantage of these customization options, you can efficiently sort data structures in a way that suits your specific needs.