qs cpp

// Program to implement quick sort in c++
#include<iostream>
using namespace std;
#define Max 30

void Quick_Sort(int data[],int first,int last);

int main()
{
    int data[Max],number_of_elements,index;

    cout<<"\nEnter your number of elements to be sorted : ";
    cin>>number_of_elements;

    // accepting string as space seperated inputs
    cout<<"\nEnter the elements:";
    for(index = 0;index < number_of_elements ;index++)
    {
        cin>>data[index];
    }

    // calling the quick sort function with first position as 0 and last position as list size -1
    Quick_Sort(data, 0, number_of_elements-1);

    // printing the sorted list
    cout<<"\nElements after sorting are :";
    for(index = 0; index < number_of_elements; index++)
    {
        cout<<data[index] <<" ";
    }
}

// recursive function to implement quick sort
void Quick_Sort(int data[],int first,int last)
{
    int pivot, left_mark, right_mark, temp;

    // checking if the array has more than one number
    if(first < last)
    {
        pivot = first;
        left_mark = first;
        right_mark = last;

        // loop while left marker is less than right marker
        while(left_mark < right_mark)
        {

            // while the data at the left mark is less than pivot keep incrementing the left_mark
            while(data[left_mark] <= data[pivot] && left_mark < right_mark)
                left_mark++;

            // while the data at the right mark is greater than pivot keep decrementing the right_mark
            while(data[right_mark] >= data[pivot] && left_mark <= right_mark)
                right_mark--;

            // swap the elements if right mark is greater than left mark
            if(right_mark > left_mark)
            {
                temp = data[right_mark];
                data[right_mark] = data[left_mark];
                data[left_mark] = temp;
            }

            // finally swap the pivot and the right mark element
            temp = data[pivot];
            data[pivot] = data[right_mark];
            data[pivot] = temp;
        }

        // make recursive calls to the function
        Quick_Sort(data, first, right_mark-1);
        Quick_Sort(data, right_mark+1, last);
    }
}