Difference Between Stdsort And Stdstable Sort Function In C++

In this article, we will discuss the difference between std::sort and std::stablesort in C++. Before discussing their differences, we must know about the std::sort and std::stablesort with their syntax, parameters, and examples.

What is the std::sort function in C++?

In C++ programming, the std::sort function is the built-in function in the Standard Template Library (STL) . It is mainly utilized to sort the elements in the range [first, last] in a desired order. It gives an easy and effective way to sort the data in C++. It may also be utilized for custom sorting by specifying in a comparator function that returns a Boolean value. This std::sort function is defined in the C++’s <algorithm> header file. It only works with data structures that allow random access to their components, like vectors and arrays .

Syntax:

It has the following syntax:

template< class RandomIter>
void sort( RandomIter first, RandomIter last, comp );

Parameters:

• ✅ template< class RandomIter>: It is the template declaration.
• ✅ void sort( RandomIter first, RandomIter last, comp ): It is the function signature for the std::sort function template in C++. RandomIter first: It represents an iterator to the first element of the range that we want to sort. RandomIter last: It represents an iterator to the past last element of the range that we want to sort. Comp (optional): A binary function, lambda expression, or functor, that compares two elements in the range.
• ✅ RandomIter first: It represents an iterator to the first element of the range that we want to sort.
• ✅ RandomIter last: It represents an iterator to the past last element of the range that we want to sort.
• ✅ Comp (optional): A binary function, lambda expression, or functor, that compares two elements in the range.

Example:

Let us take an example to illustrate the std::sort function in C++.

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

int main() {
  std::vector<int> Num{45, 37, 55, 22, 68, 19, 44};

  // Sorting using std::sort
  std::sort(Num.begin(), Num.end());

  // Printing the sorted vector
  for (const int& x: Num) {
    std::cout << x<< " ";
  }
}

Output:

19 22 37 44 45 55 68

What is the std::stable_sort function in C++?

The std::stablesort function is also utilized to sort the elements in the range [first, last] in the ascending order. It is similar to the std::sort function, but it preserves the desired order of equivalent elements. This std::stablesort function is defined in the C++’s <algorithm> header file.

Syntax:

It has the following syntax:

template< class RandomIter>
void stable_sort( RandomIter first, RandomIter last );

and the other syntax is:

template< class RandomIter, class Compare>
void stable_sort( RandomIter first, RandomIter last, Compare comp );

Parameters:

• ✅ template< class RandomIter>: It is the template declaration.
• ✅ void sort( RandomIter first, RandomIter last, comp ): It is the function signature for the std::stable_sort function template in C++. RandomIter first: It represents an iterator to the first element in the range. RandomIter last: It represents an iterator to the past last element in the range. Comp: It accepts two arguments and returns true if two inputs in order; otherwise, it returns false.
• ✅ RandomIter first: It represents an iterator to the first element in the range.
• ✅ RandomIter last: It represents an iterator to the past last element in the range.
• ✅ Comp: It accepts two arguments and returns true if two inputs in order; otherwise, it returns false.

Return Value:

It does not return any value.

Example:

Let us take an example to illustrate the std::stable_sort function in C++.

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

struct Employee {
  std::string name;
  int Department;

  // Comparison operator for sorting by department
  bool operator<(const Employee& other) const {
    if (Department == other.Department) {
      return name < other.name; 
    }
    return Department < other.Department; 
  }
};

int main() {
  std::vector<Employee> employees{
    {"Alice", 2},
     {"Grace", 2},
    {"Charlie", 2},
    {"David", 1},
    {"Eve", 3},
    {"Bob", 1},
    {"Frank", 3}
  };

  // Sorting employees by department 
  std::stable_sort(employees.begin(), employees.end());

  // Print the sorted employees
  std::cout << "Sorted Employees:\n";
  for (const Employee& emp : employees) {
    std::cout << emp.name << " (Dept " << emp.Department << ")\n";
  }

  return 0;
}

Output:

Sorted Employees:
Bob (Dept 1)
David (Dept 1)
Alice (Dept 2)
Charlie (Dept 2)
Grace (Dept 2)
Eve (Dept 3)
Frank (Dept 3)

Key differences between std::sort and std::stable_sort function in C++:

There are several key differences between std::sort and std::stable_sort in C++. Some main differences are as follows:

Conclusion:

In conclusion, the std::sort and std::stable_sort functions are important functions in C++ . Both functions are used to sort the elements in a desired order. Understanding the differences between these algorithms assists in picking the best one for our requirements. It ensures the efficiency and correctness of our program. We may get the best algorithm according to our requirements.