quick_sort.c

#include <stdio.h>

void swap(int *a, int *b) {
  int t = *a;
  *a = *b;
  *b = t;
}

int partition(int array[], int low, int high) {
  
  int pivot = array[high];
  
  int i = (low - 1);

  for (int j = low; j < high; j++) {
    if (array[j] <= pivot) {
        
      i++;
      
      swap(&array[i], &array[j]);
    }
  }

  swap(&array[i + 1], &array[high]);
  
  return (i + 1);
}

void quickSort(int array[], int low, int high) {
  if (low < high) {

    int pi = partition(array, low, high);
    
    quickSort(array, low, pi - 1);
    
    quickSort(array, pi + 1, high);
  }
}

void printArray(int array[], int size) {
  for (int i = 0; i < size; ++i) {
    printf("%d  ", array[i]);
  }
  printf("\n");
}

int main() 
{
  int items[] = {21, 10, 42, 11, 3, 7, 19};
  
  int n = sizeof(items) / sizeof(items[0]);
  
  printf("Unsorted Array\n");
    for (int i = 0; i < n; ++i) 
    {
        printf("%d  ", items[i]);
    }
  printf("\n\n");  

  quickSort(items, 0, n - 1);
  
  printf("Sorted array in ascending order: \n");
  printArray(items, n);
}