Quick sort can be very useful to you if you want to sort your array efficiently.

The Time complexities for quick sort
Best Case performance        : O(n log n)
Average Case Performance : O(n log n)
Worst Case Performance     : O(n²)

Quicksort is a divide and conquer algorithm. Quicksort first divides a large array into two smaller sub-arrays: the low elements and the high elements. Quicksort can then recursively sort the sub-arrays.

Following is the declaration for qsort() function.

void qsort(void base, size_t nitems, size_t size, int (compar)(const void , const void))


Demo Program:

#include <stdio.h>
#include <stdlib.h>

int values[] = { 88, 56, 100, 2, 25 };

int cmpfunc (const void * a, const void * b)
{
   return ( *(int*)a - *(int*)b );
}

int main()
{
   int n;

   printf("Before sorting the list is: \n");
   for( n = 0 ; n < 5; n++ ) 
   {
      printf("%d ", values[n]);
   }

   qsort(values, 5, sizeof(int), cmpfunc);

   printf("\nAfter sorting the list is: \n");
   for( n = 0 ; n < 5; n++ ) 
   {   
      printf("%d ", values[n]);
   }

   return(0);
}

Output

Before sorting the list is: 
88 56 100 2 25
After sorting the list is:
2 25 56 88 100