In many programming tasks, we often encounter situations where we need to sort a collection of elements based on specific criteria. The standard C++ library provides us with the std::sort function to sort elements using default comparison operators. However, there are cases where we might want to define our own custom sorting order.
In this blog post, we will explore how to implement custom sorting literals in C++. By using custom comparison functions or function objects, we can define our own rules for sorting elements within a collection.
Using Custom Comparison Function
One way to implement custom sorting literals is by using a custom comparison function. This function should take two elements as input parameters and return true if the first element should come before the second element in the sorted order, or false otherwise.
Let’s say we have a collection of strings and we want to sort them based on their length. We can define a custom comparison function that compares the lengths of two strings:
bool compareLength(const std::string& str1, const std::string& str2) {
return str1.length() < str2.length();
}
We can then pass this custom comparison function as the third argument to the std::sort function, along with the begin and end iterators of our collection:
std::vector<std::string> strings = { "apple", "banana", "cherry", "date" };
std::sort(strings.begin(), strings.end(), compareLength);
After sorting, the strings vector will contain the elements in the following order: date, apple, cherry, banana. The elements are sorted based on their length.
Using Custom Comparison Function Object
Alternatively, we can use a custom comparison function object instead of a function. A function object is a class that overloads the operator() to define the comparison behavior. This allows us to create objects that behave as functions.
Let’s rewrite our previous example using a custom comparison function object:
struct CompareLength {
bool operator()(const std::string& str1, const std::string& str2) const {
return str1.length() < str2.length();
}
};
We can then create an instance of this class and pass it as the third argument to std::sort:
std::vector<std::string> strings = { "apple", "banana", "cherry", "date" };
std::sort(strings.begin(), strings.end(), CompareLength());
The result will be the same as before, with the strings vector sorted based on the length of the elements.
Conclusion
Custom sorting literals allow us to define our own rules for sorting elements in C++. By using custom comparison functions or function objects, we can sort elements based on any criteria we desire.
In this blog post, we explored how to use custom comparison functions and function objects to implement custom sorting literals in C++. This gives us the flexibility to sort elements based on any custom logic we need.
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