using namespace std;
#include<iostream>
#include<stdlib.h>
#include<time.h>

/*
  Timing the performance of the built-in quicksort function

  type "man qsort" on any unix/linux prompt for information
*/

// function to compare two integers:
int comp(const void *x, const void *y)
{ int a, b;
  a = *((const int*)x);
  b = *((const int*)y);
  return  a-b;
}


int main(int argc, char** argv)
{
  int n;  // size of array, determined by command-line argument
  int *A; // array to be dynamically created
  clock_t t1, t2;  // for time measurements
  n = atoi(argv[1]);   // first command-line argument
  A = new int[n];
  for(int i=0;i<n;i++) A[i] = (int) random();
 
  t1 = clock();
  qsort(A, (size_t)n, (size_t)(sizeof(int)), comp);
  // quicksort
  t2 = clock();

  delete(A);
  cout << "\ntime ~= " << (t2-t1)/((double)CLOCKS_PER_SEC) << " seconds\n";
  return 0;  
}