How is the data sorting procedure implemented in standard libraries?

In standard C and C++ libraries, sorting is usually implemented using the QuickSort algorithm or its variations.

• In C, the standard function qsort implements quicksort using recursion and partitioning the array into subarrays.
• In C++, the std::sort function from <algorithm> typically uses a hybrid algorithm called Introsort, which combines quicksort, heapsort, and insertion sort for optimal performance and stability.

Example of using qsort in C:

#include <stdlib.h>

int compare(const void *a, const void *b) {
    int int_a = *(int*)a;
    int int_b = *(int*)b;
    return (int_a > int_b) - (int_a < int_b);
}

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

Thus, sorting in standard libraries is based on efficient algorithms with optimizations for different cases.