C++ cstdlib qsort()

qsort() is a standard library C++ cstdlib qsort() (from the cstdlib header) that implements the quicksort algorithm. It allows sorting an array of elements using a user-defined comparison function.

Syntax:

void qsort(void* base, size_t num, size_t size, int (*compar)(const void*, const void*));

Parameters:

base: Pointer to the first element of the array.

num: Number of elements in the array.

size: Size of each element in bytes.

compar: Pointer to the comparison function, which determines the order of elements.

Usage Example:

#include <cstdlib>

#include <iostream>

int compare(const void* a, const void* b) {

    return (*(int*)a - *(int*)b);

}

int main() {

    int arr[] = {3, 1, 4, 1, 5, 9};

    size_t size = sizeof(arr) / sizeof(arr[0]);

    qsort(arr, size, sizeof(int), compare);

    for (int i = 0; i < size; i++) {

        std::cout << arr[i] << " ";

    }

    return 0;

}

Key Points:fv

qsort() is useful for sorting arrays of any type by customizing the comparison function.

Use caution with typecasting in the comparison function.