Question

please write a C program that implements Quick Sort algorithm.

Answer 1

Quicksort is an algorithm for Divide and Conquer. The steps are as follows: 1) Pick an element from the array that is called as a pivot element. 2) Divide the unsorted array of elements into two arrays with values less than the pivot in the first sub-array, while the second sub-array contains all elements with values greater than the pivot. The partition operation is called this step. 3) Repeat step 2 (until the sub-arrays are sorted) recursively to the sub-array of elements with smaller values and to the sub-array of elements with larger values separately. The same logic that we implemented in the following C program.

C Program for Quicksort algorithm implementation.

#include<stdio.h>
void quicksort(int number[25],int first,int last){
   int i, j, pivot, temp;

   if(first<last){
      pivot=first;
      i=first;
      j=last;

      while(i<j){
         while(number[i]<=number[pivot]&&i<last)
            i++;
         while(number[j]>number[pivot])
            j--;
         if(i<j){
            temp=number[i];
            number[i]=number[j];
            number[j]=temp;
         }
      }

      temp=number[pivot];
      number[pivot]=number[j];
      number[j]=temp;
      quicksort(number,first,j-1);
      quicksort(number,j+1,last);

   }
}

int main(){
   int i, count, number[25];

   printf("How many elements are you going to enter?: ");
   scanf("%d",&count);

   printf("Enter %d elements: ", count);
   for(i=0;i<count;i++)
      scanf("%d",&number[i]);

   quicksort(number,0,count-1);

   printf("Sorted elements: ");
   for(i=0;i<count;i++)
      printf(" %d",number[i]);

   return 0;
}

Output