ЗАмерение времени

#include <iostream>
#include "time.h"
#include "random"
#include "fstream"

using namespace std;
void qsort(int * a, int n){
    int c = a[rand()%n];
    int l=0;
    int r = n-1;
    do{
        while(a[l]<c) l++;
        while(a[r]>c) r--;
        if (l<=r){
            swap(a[l],a[r]);
            l++;
            r--;
        }

    }
    while (l<=r);
    if (l<n){
        qsort(a+l,n-l);
    }
    if (r>0){
        qsort(a,r+1);
    }
}

int main()
{
    ofstream myfile;
    int n;
    cin>>n;
    int *a = new int[n];
    myfile.open ("example.txt");
    for (int k=0;k<10;k++){
        for (int x=0;x<n;x++){
            a[x]=rand()%1000;
        }
        int t1=clock();
        qsort(a,n);
        int t2=clock();
        myfile <<t2-t1<<"\n";
    }
    myfile.close();
    return 0;
}