Array Sorting Function In C++

MUAZHAN

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Jun 28, 2024

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Array Sorting Functions in C++

C++ provides several built-in functions for sorting arrays, making it easy to organize data in ascending or descending order. Here are some of the most commonly used sorting functions:

1. std::sort()

This function is part of the <algorithm> header file and offers a highly efficient sorting algorithm.

Syntax:

#include 
#include 

int main() {
  int arr[] = {5, 2, 9, 1, 5};
  int n = sizeof(arr) / sizeof(arr[0]);

  std::sort(arr, arr + n); // sorts in ascending order

  for (int i = 0; i < n; i++) {
    std::cout << arr[i] << " ";
  }
  std::cout << std::endl;

  return 0;
}

Explanation:

• std::sort(arr, arr + n): This line sorts the array arr from the beginning (arr) to the end (arr + n).
• The function sorts the array in ascending order by default.
• To sort in descending order, use std::sort(arr, arr + n, std::greater<int>());.

2. std::stable_sort()

This function is similar to std::sort() but guarantees that elements with the same value maintain their relative order.

Syntax:

#include 
#include 

int main() {
  int arr[] = {5, 2, 9, 1, 5};
  int n = sizeof(arr) / sizeof(arr[0]);

  std::stable_sort(arr, arr + n);

  for (int i = 0; i < n; i++) {
    std::cout << arr[i] << " ";
  }
  std::cout << std::endl;

  return 0;
}

Explanation:

• std::stable_sort(arr, arr + n): This line sorts the array arr while preserving the relative order of elements with the same value.

3. std::qsort()

This function is from the <cstdlib> header file and uses the quicksort algorithm for sorting.

Syntax:

#include 
#include 

int compare(const void* a, const void* b) {
  return (*(int*)a - *(int*)b);
}

int main() {
  int arr[] = {5, 2, 9, 1, 5};
  int n = sizeof(arr) / sizeof(arr[0]);

  qsort(arr, n, sizeof(arr[0]), compare);

  for (int i = 0; i < n; i++) {
    std::cout << arr[i] << " ";
  }
  std::cout << std::endl;

  return 0;
}

Explanation:

• qsort(arr, n, sizeof(arr[0]), compare): This line sorts the array arr using quicksort algorithm.
• compare is a custom function to define the sorting criteria (ascending order in this case).

Remember:

• std::sort() and std::stable_sort() are typically preferred due to their efficiency and ease of use.
• std::qsort() is generally less efficient than the algorithms used by std::sort() and std::stable_sort().

These sorting functions provide powerful tools for organizing data in C++. Choosing the appropriate function depends on your specific needs and the characteristics of your data.