Question

I was given the following HomeWork assignment,

Write a program to test on your computer how long it takes to do
nlogn, n2, n5, 2n, and n! additions for n=5, 10, 15, 20.

I have written a piece of code but all the time I am getting the time of execution 0. Can anyone help me out with it? Thanks

#include <iostream>
#include <cmath>
#include <ctime>
using namespace std;
int main()
{
 float n=20;
 time_t start, end, diff;
  start = time (NULL);
  cout<<(n*log(n))*(n*n)*(pow(n,5))*(pow(2,n))<<endl;
  end= time(NULL);
 diff = difftime (end,start);
 cout <<diff<<endl;
 return 0;
}

Answer 1

Execute each calculation thousands of times, in a loop, so that you can overcome the low resolution of time and obtain meaningful results. Remember to divide by the number of iterations when reporting results.

This is not particularly accurate but that probably does not matter for this assignment.