in place quicksort

qs.cpp

#include <iostream>
#include <vector>

using namespace std;

void print(vector<int> a) {
    for (int el : a) {
        cout << el << " ";
    }
    cout << endl;
}

void swap(vector<int>& arr, int i, int j) {
    int temp = arr[i];
    arr[i] = arr[j];
    arr[j] = temp;
}

vector<int> in_place_quick_sort(vector<int>& arr, int start, int end) {
    if (end - start <= 2) {
        return arr;
    }
    int pivot_idx = start + (end - start) / 2;
    int pivot_val = arr[pivot_idx];

    int lcursor = start;
    int rcursor = pivot_idx + 1;
    while (lcursor < pivot_idx || rcursor < end) {
        if (lcursor < pivot_idx) {
            if (arr[lcursor] > pivot_val) {
                swap(arr, pivot_idx, lcursor);
                swap(arr, lcursor, --pivot_idx);
            }

            lcursor < pivot_idx ? ++lcursor : --lcursor;
        } else if (rcursor < end) {
            if (arr[rcursor] < pivot_val) {
                swap(arr, pivot_idx, rcursor);
                swap(arr, rcursor, ++pivot_idx);
                lcursor++;
            }
            rcursor++;
        }
    }
    print(arr);
    in_place_quick_sort(arr, start, pivot_idx);
    in_place_quick_sort(arr, pivot_idx, end);
    return arr;
}

vector<int> quick_sort(vector<int> arr) {
    return in_place_quick_sort(arr, 0, arr.size());
}


int main() {
    vector<int> test{300, 4,5,3,8,3,6,7,1,3,1,6,-1,11,232};
    print(quick_sort(test));
    return 0;
}