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C stdlib qsort() Function

❮ C stdlib Library


Example

Sort an array:

// Comparing function:
// Returns a positive number if a is greater than b
// Returns a negative number if a is less than b
// Returns 0 if a is equal to b
int compare(const void *a, const void *b) {
  int *valA = a;
  int *valB = b;
  return *valA - *valB;
}

int main() {
  // Create an array
  int myArray[] = {20, 32, 5, 2, 24, 15};
  int size = sizeof(myArray) / sizeof(myArray[0]);

  // Sort the values in the array
  qsort (myArray, size, sizeof(myArray[0]), compare);

  // Display the values of the array
  for(int i = 0; i < size; i++) {
    printf("%d ", myArray[i]);
  }

  return 0;
}
Try it Yourself »

Definition and Usage

The qsort() function sorts the elements in an array from least to greatest.

The qsort() function is defined in the <stdlib.h> header file.


Syntax

qsort(void * arr, size_t amount, size_t size, compare);

The size_t data type is a non-negative integer.

Parameter Values

Parameter Description
arr Required. Specifies the array to be sorted.
amount Required. Specifies the number of elements in the array.
size Required. Specifies the size of an element in the array measured in bytes.
compare Required. Specifies a function used to compare pairs of elements in the array to determine which one is greater.
The function should have the structure int myFunction(const void * a, const void * b) where the parameters a and b are pointers to elements in the array being compared.
The function should return a positive number if a is greater than b, a negative number if a is less than b and zero if a and b are equal.

❮ C stdlib Library

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