Сортировка массива

#include <iostream>
#include <vector>
 
using namespace std;
 
void vec_sort(vector<int>& arr, int first, int last)
{
    int tmp;
    int i = first, j = last;
    int x = rand() % 20 + 1;
    do
    {
        while (arr[i] < x) i++;
        while (arr[j] > x) j--;
        if (i <= j) 
        {
            tmp = arr[i];
            arr[i] = arr[j];
            arr[j] = tmp;
            i++;
            j--;
        }
    } while (i<j);
    
    if (first < j) vec_sort(arr, first, j);
    if (i < last) vec_sort(arr, i, last);
}
 
int main(int argc, const char * argv[]) {
    int size = rand() % 10 + 1;
    cout << "size: " << size << endl;
    
    vector<int> arr(size);
    
    for( int i = 0; i < size; ++i )
        arr[i] = rand() % 20 + 1;
 
    cout << endl << "-- Basic Array --" << endl;
    for (int i = 0; i < arr.size(); i++)
        cout << arr[i] << " ";
    cout << endl << endl;
    
    cout << "-- Sorted Array --" << endl;
    vec_sort(arr, 0, size - 1);
    
    for (int i = 0; i < arr.size(); i++)
        cout << arr[i] << " ";
    cout << endl << endl;
    
    return 0;
}

void vec_sort(vector<double>& arr, double x)
{
    int tmp;
    int leftRead = 0, rightRead = arr.size() - 1;
    int leftWrite = leftRead, rightWrite = rightRead;
 
    do
    {
        while (leftRead < rightRead && arr[leftRead] <= x) {
            if (arr[leftRead] < x) {
                arr[leftWrite++] = arr[leftRead];
            }
            leftRead++;
        }
        while (leftRead < rightRead && arr[rightRead] >= x) {
            if (arr[rightRead] > x) {
                arr[rightWrite--] = arr[rightRead];
            }
            rightRead--;
        }
 
        if (leftRead < rightRead) {
            tmp = arr[leftRead];
            arr[leftWrite++] = arr[rightRead];
            arr[rightWrite--] = tmp;
        } else if (leftRead == rightRead) {
            if (arr[leftRead] < x) {
                arr[leftWrite++] = arr[leftRead];
            } else if (arr[leftRead] > x) {
                arr[rightWrite--] = arr[leftRead];
            }
        }
        leftRead++;
        rightRead--;
    } while (leftRead <= rightRead);
 
    while (leftWrite <= rightWrite) {
        arr[leftWrite++] = x;
    }
}