std::qsort

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

Algorithm library

Constrained algorithms and algorithms on ranges (C++20)
Constrained algorithms, e.g. ranges::copy, ranges::sort, ...
Execution policies (C++17)
is_execution_policy (C++17)   execution::seqexecution::parexecution::par_unseqexecution::unseq (C++17)    (C++17)(C++17)(C++20)	execution::sequenced_policyexecution::parallel_policyexecution::parallel_unsequenced_policyexecution::parallel_unsequenced (C++17)(C++17)(C++17)(C++20)
Non-modifying sequence operations Batch operations for_each for_each_n (C++17) Search operations all_ofany_ofnone_of (C++11)                (C++11)(C++11) countcount_if mismatch equal findfind_iffind_if_not (C++11) find_end find_first_of adjacent_find search search_n Modifying sequence operations Copy operations copycopy_if (C++11) copy_backward copy_n (C++11) move (C++11) move_backward (C++11) Swap operations swap iter_swap swap_ranges Transformation operations replacereplace_if transform replace_copyreplace_copy_if Generation operations fill fill_n generate generate_n Removing operations removeremove_if unique remove_copyremove_copy_if unique_copy Order-changing operations reverse reverse_copy rotate rotate_copy random_shuffleshuffle (until C++17)(C++11) shift_leftshift_right (C++20)(C++20) Sampling operations sample (C++17)	Sorting and related operations Partitioning operations partition partition_copy (C++11)   stable_partition is_partitioned (C++11) partition_point (C++11) Sorting operations sort stable_sort partial_sort partial_sort_copy is_sorted (C++11) is_sorted_until (C++11) nth_element Binary search operations (on partitioned ranges) lower_bound upper_bound equal_range binary_search Set operations (on sorted ranges) includes set_union set_intersection set_difference set_symmetric_difference Merge operations (on sorted ranges) merge inplace_merge Heap operations push_heap pop_heap make_heap sort_heap is_heap (C++11) is_heap_until (C++11) Minimum/maximum operations max min minmax (C++11) clamp (C++17) max_element min_element minmax_element (C++11) Lexicographical comparison operations lexicographical_compare lexicographical_compare_three_way (C++20) Permutation operations next_permutation prev_permutation is_permutation (C++11) C library qsort bsearch
Numeric operations
iota (C++11) inner_product adjacent_difference    accumulate reduce (C++17) transform_reduce (C++17)	partial_sum inclusive_scan (C++17)    exclusive_scan (C++17) transform_inclusive_scan (C++17) transform_exclusive_scan (C++17)
Operations on uninitialized memory
uninitialized_copy uninitialized_move (C++17)    uninitialized_fill uninitialized_copy_n (C++11) uninitialized_move_n (C++17) uninitialized_fill_n	destroy (C++17) destroy_n (C++17) destroy_at (C++17) construct_at (C++20)       uninitialized_default_construct (C++17) uninitialized_value_construct (C++17) uninitialized_default_construct_n (C++17) uninitialized_value_construct_n (C++17)

 

Template:ddcl list begin <tr class="t-dsc-header">

<td>

Defined in header <cstdlib>

</td>

<td></td> <td></td> </tr> <tr class="t-dcl ">

<td class="t-dcl-nopad">

void qsort( const void *ptr, size_t count, size_t size,
            int (*comp)(const void *, const void *) );

</td>

<td class="t-dcl-nopad"> </td> <td class="t-dcl-nopad"> </td> </tr> Template:ddcl list end

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

Parameters

ptr	-	pointer to the array to sort
count	-	number of element in the array
size	-	size of each element in the array in bytes
comp	-	comparison function which returns ​a 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. ​

Return value

(none)

Notes

The type of the elements of the array must be a trivial type, otherwise the behavior is undefined.

Example

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

Run this code

#include <iostream>
#include <cstdlib>
 
int compare_ints(const void* a, const void* b)   // comparison function
{
    int* arg1 = (int*) a;
    int* arg2 = (int*) b;
    if (*arg1 < *arg2) return -1;
    else if (*arg1 == *arg2) return 0;
    else return 1;
}
 
int main()
{
    int a[] = { -2, 99, 0, -743, 2, 3, 4 };
    int size = 7;
 
    std::qsort(a, size, sizeof(int), compare_ints);
 
    for (int i = 0; i < size; i++) {
        std::cout << a[i] << " ";
    }
    std::cout << '\n';
}

Output:

-743 -2 0 2 3 4 99

See also

Template:cpp/algorithm/dcl list bsearchTemplate:cpp/algorithm/dcl list sort

is_trivial (C++11)	checks if a type is trivial (class template)
C documentation for qsort