RetroSearch Browse

Home - News ( United States | United Kingdom | Italy | Germany ) - Football scores

Showing content from https://en.cppreference.com/w/cpp/language/../keyword/../language/../algorithm/qsort.html below:

std::qsort - cppreference.com

(1)

extern "C" using /* c-compare-pred */ = int(const void*, const void*); extern "C++" using /* compare-pred */ = int(const void*, const void*);

(2) (exposition only*)

Sorts the given array pointed to by ptr in ascending order. The array contains count elements of size bytes. Function pointed to by comp is used for object comparison.

If comp indicates two elements as equivalent, their order is unspecified.

If the type of the elements of the array is not a PODType(until C++11)TriviallyCopyable type(since C++11), the behavior is undefined.

[edit] Parameters ptr - pointer to the array to sort count - number of elements in the array size - size of each element in the array in bytes comp - comparison function which returns âa negative integer value if the first argument is less than the second, a positive integer value if the first argument is greater than the second and zero if the arguments are equivalent.

The signature of the comparison function should be equivalent to the following:

int cmp(const void *a, const void *b);

The function must not modify the objects passed to it and must return consistent results when called for the same objects, regardless of their positions in the array.

[edit] Return value

(none)

[edit] Notes

Despite the name, C++, C, and POSIX standards do not require this function to be implemented using Quicksort or make any complexity or stability guarantees.

The two overloads provided by the C++ standard library are distinct because the types of the parameter comp are distinct (language linkage is part of its type).

[edit] Example

The following code sorts an array of integers using qsort():

#include <array>
#include <climits>
#include <compare>
#include <cstdlib>
#include <iostream>
 
int main()
{
    std::array a{-2, 99, 0, -743, INT_MAX, 2, INT_MIN, 4};
 
    std::qsort
    (
        a.data(),
        a.size(),
        sizeof(decltype(a)::value_type),
        [](const void* x, const void* y)
        {
            const int arg1 = *static_cast<const int*>(x);
            const int arg2 = *static_cast<const int*>(y);
            const auto cmp = arg1 <=> arg2;
            if (cmp < 0)
                return -1;
            if (cmp > 0)
                return 1;
            return 0;
        }
    );
 
    for (int ai : a)
        std::cout << ai << ' ';
    std::cout << '\n';
}

Output:

-2147483648 -743 -2 0 2 4 99 2147483647

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior LWG 405 C++98 the elements of the array could have any type limited to PODType [edit] See also

RetroSearch is an open source project built by @garambo | Open a GitHub Issue

Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo

HTML: 3.2 | Encoding: UTF-8 | Version: 0.7.4