nbodycode

#include <iostream>
#include <ctime>
#include <math.h>
using namespace std;
#define N 100
#define G 6.673e-11
#define TIMESTAMP 1e11
struct Particle{
    double rx, ry;//position components
    double vx, vy;//velocity components
    double fx, fy;//force components
    double mass;//mass of the particle

};
Particle Update(Particle p, double timestamp)
{
    p.vx += timestamp*p.fx / p.mass;
    p.vy += timestamp*p.fy / p.mass;
    p.rx += timestamp*p.vx;
    p.ry += timestamp*p.vy;
    return p;
}
void PrintParticle(Particle p)
{
    printf("rx == %f ry == %f vx == %f vy == %f mass == %f\n", p.rx,p.ry,p.vx,p.vy,p.mass);
}
//Reset the forces on particle
Particle ResetForce(Particle p)
{
    p.fx = 0.0;
    p.fy = 0.0;
    return p;
}
//Add force to particle a by particle b
Particle AddForce(Particle a,Particle b)
{
    double EPS = 3E4;      // softening parameter (just to avoid infinities)
    double dx = b.rx - a.rx;
    double dy = b.ry - a.ry;
    double dist = sqrt(dx*dx + dy*dy);
    double F = (G * a.mass * b.mass) / (dist*dist + EPS*EPS);
    a.fx += F * dx / dist;
    a.fy += F * dy / dist;
    return a;

}

int main()
{
    Particle particles[N];
    srand(time(NULL));
    //randomly generating N Particles
    for (int i = 0; i < N; i++){
        double rx = 1e18*exp(-1.8)*(.5 - rand());
        particles[i].rx = rx;
        double ry = 1e18*exp(-1.8)*(.5 - rand());
        particles[i].ry = ry;
        double vx = 1e18*exp(-1.8)*(.5 - rand());
        particles[i].vx = vx;
        double vy = 1e18*exp(-1.8)*(.5 - rand());
        particles[i].vy = vy;
        double mass = 1.98892e30*rand()*10 + 1e20;
        particles[i].mass = mass;

    }

    int numberofiterations = 10;
    int count = 0;
    while (count < numberofiterations){
        for (int i = 0; i < N; i++)
        {
            particles[i] = ResetForce(particles[i]);
            for (int j = 0; j < N; j++)
            {
                if (i != j)
                {
                    particles[i] = AddForce(particles[i], particles[j]);
                }

            }
        }
        //loop again to update the time stamp here
        for (int i = 0; i < N; i++)
        {
            particles[i] = Update(particles[i], TIMESTAMP);
        }
        for (int i = 0; i < N; i++)
        {
            PrintParticle(particles[i]);
        }
        count++;
    }




    return 0;
}