Quicksort

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
int partition(int arr[],int left,int right)
{
    int x = arr[right]; //initialize comparing value
    int i = left-1;
    //exchanging elements if necessary or exchange with themselves
    for(int j=left;j<=right-1;j++)
    {
        if(arr[j]<x)
        {
            i++;
            swap(arr[i],arr[j]);
        }
    }
    //exchange with compared value to put it on the right place
    swap(arr[i+1],arr[right]);
    return i+1; //return the index
}

void quicksort(int arr[],int left,int right)
{
    //base case
    if(left>=right)
        return;
    //process
    int q = partition(arr,left,right); //partitioning index
    //recursive call
    quicksort(arr,left,q-1);
    quicksort(arr,q+1,right);
}

int main()
{
    #ifndef ONLINE_JUDGE
        freopen("input.txt", "r", stdin);
        freopen("output.txt", "w", stdout);
    #endif

    int n;
    cin >> n; //declaring array size
    int arr[n]; //declaring array
    for(int i=0;i<n;i++)
        cin >> arr[i];
    //calling function
    quicksort(arr,0,n-1);
    //printing array
    for(int i=0;i<n;i++)
        cout << arr[i] << ' ';

    return 0;
}