Difference between revisions of "c/algorithm/qsort"
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| − | Sorts the given array pointed to by {{tt|ptr}} in ascending order. The array contains {{tt|count}} elements of | + | Sorts the given array pointed to by {{tt|ptr}} in ascending order. The array contains {{tt|count}} elements of {{tt|size}} bytes. Function pointed to by {{tt|comp}} is used for object comparison. |
If {{tt|comp}} indicates two elements as equivalent, their order is undefined. | If {{tt|comp}} indicates two elements as equivalent, their order is undefined. | ||
Revision as of 23:59, 22 April 2013
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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 undefined.
Contents |
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)
Example
The following code sorts an array of integers using qsort()
#include <stdio.h> #include <stdlib.h> int compare_ints(const void* a, const void* b) { const int *arg1 = a; const int *arg2 = b; return *arg1 - *arg2; } int main(void) { int i; int ints[] = { -2, 99, 0, -743, 2, 3, 4 }; int size = sizeof ints / sizeof *ints; qsort(ints, size, sizeof(int), compare_ints); for (i = 0; i < size; i++) { printf("%d ", ints[i]); } printf("\n"); return EXIT_SUCCESS; }
Output:
-743 -2 0 2 3 4 99
See also
| C++ documentation for qsort
|
