Quick Sort in CPP

 #include<iostream>

using namespace std;

int getPivotInd(int arr[],int l,int r){

    int pivot=arr[l];

    // Make j equal to the last index and i equal to "last index+1" index

    int j=r,i=r+1;

    int size=r+1-l;

    cout<<"Array received:\t";

    for(int i=l;i<=r;i++){

        cout<<arr[i]<<" ";

    }

    cout<<endl;

    cout<<"Pivot Value: "<<pivot<<"\tjth index: "<<j<<"\tith index: "<<i<<endl;

    while(j>l){

        if(arr[j]>=pivot){

            cout<<"jth elem is greater than pivot elem:\t"<<arr[j]<<">="<<pivot<<endl;

            int temp;

            // Decrease i and swap jth elem with ith elem

            i--;

            cout<<"Swapping ith elem: "<<arr[i]<<" with the jth elem: "<<arr[j]<<"\n";

            temp=arr[j];

            arr[j]=arr[i];

            arr[i]=temp;

        }

        j--;

    }

    cout<<"Loop Complete, now swapping elem before i that is "<<arr[i-1]<<"\t"

    "with pivot that is "<<arr[l]<<endl;

    // Now as the loop is complete, decrease i and then swap with the first elem,

    // that is the pivot elem(at index l)

    i--;

    int temp=arr[i];

    arr[i]=arr[l];

    // Now the pivot is at the ith ind

    arr[l]=temp;

    cout<<"Array after placing pivot at correct position:\t";

    for(int i=l;i<=r;i++){

        cout<<arr[i]<<" ";

    }

    cout<<"\n\n";

   

    // Returns the index of the pivot elem, now that pivot is swapped with the

    // ith elem, pivot is at ith index

    return i;

}

// Here l and r are the extreme indices(first and last index) of the array provided

void quickSort(int arr[],int l,int r){

    // Will do anything only if there are atleast 2 elements, otherwise just

    // ignore it

    if(l<r){

        // Get the index of the pivot, that index will be the final index of

        // the pivot elem

        int pivotInd=getPivotInd(arr,l,r);

        // Now we just need to sort the array before pivot

        quickSort(arr,l,pivotInd-1);

        // And array after pivot

        quickSort(arr,pivotInd+1,r);

    }

    else{

        // Just ignore, bcz 1 elem or 0 elems are already sorted

    }

}

int main(){

    int arr[]={10,16,8,12,15,6,3,9,5};

    // cout<<"Hello? World?\n";

    quickSort(arr,0,8);

   // Array after sorting

    // cout<<*arr<<endl;

    // cout<<sizeof(arr)<<endl;

    for(int i=0;i<sizeof(arr)/sizeof(int);i++){

        cout<<arr[i]<<" ";

    }

    // for(int i=0;i<5;i++){

    //     // cout<<"elem: "<<*arr<<" and i: "<<i<<endl;

    //     cout<<*arr+i<<endl;

    //     // cout<<*(arr+i)<<" ";

    // }

    return 0;

}