File talk:Quicksort-diagram.svg

1. include <stdio.h>
2. include <stdlib.h>

void swap(int *x,int *y) {

  int temp;
  temp = *x;
  *x = *y;
  *y = temp;

}

int choose_pivot(int i,int j ) {

  return((i+j) /2);

}

void quicksort(int list[],int m,int n) {

  int key,i,j,k;
  if( m < n)
  {
     k = choose_pivot(m,n);
     swap(&list[m],&list[k]);
     key = list[m];
     i = m+1;
     j = n;
     while(i <= j)
     {
        while((i <= n) && (list[i] <= key))
               i++;
        while((j >= m) && (list[j] > key))
               j--;
        if( i < j)
               swap(&list[i],&list[j]);
     }

// swap two elements

     swap(&list[m],&list[j]);

// recursively sort the lesser list

     quicksort(list,m,j-1);
     quicksort(list,j+1,n);
  }

} void printlist(int list[],int n) {

  int i;
  for(i=0;i<n;i++)
     printf("%d\t",list[i]);

}

void main() {

  const int MAX_ELEMENTS = 10;
  int list[MAX_ELEMENTS];

  int i = 0;
  
  // generate random numbers and fill them to the list
  for(i = 0; i < MAX_ELEMENTS; i++ ){

list[i] = rand();

  }
  printf("The list before sorting is:\n");
  printlist(list,MAX_ELEMENTS);
  
  // sort the list using quicksort
  quicksort(list,0,MAX_ELEMENTS-1);

  // print the result
  printf("The list after sorting using quicksort algorithm:\n");
  printlist(list,MAX_ELEMENTS);

}