Vanilla Option Pricing via C++

Box-Muller Algorithm, generate Gaussian random numbers

#ifndef BM_GAUSSIAN_HPP_INCLUDED
#define BM_GAUSSIAN_HPP_INCLUDED

#include <cstdlib>
#include <cmath>
#include <vector>

double uniformRandom(){
return (double)(rand()+1.0)/(double)(RAND_MAX+1.0);
}

void normalRandom(std::vector<double>& v){
double u1=uniformRandom();
double u2=uniformRandom();

v[0] = cos(8.0*atan(1.0)*u2)*sqrt(-2.0*log(u1));
v[1] = sin(8.0*atan(1.0)*u1)*sqrt(-2.0*log(u2));
}

#endif // BM_GAUSSIAN_HPP_INCLUDED

main function
#include <iostream>
#include <cstdlib>
#include <cmath>
#include <vector>
#include <./BM_Gaussian.hpp>
using namespace std;

int main(){
// set option contract parameters;
double T = 1.0;
double K = 100;
double S0 = 100;
double sigma = 0.1;
double r = 0.01;

int npaths = 100000;
int nsteps = 100/2;

double S;
vector<double> rnorm(2);
double sumpayoff = 0.0;
double dt = double(T)/double(nsteps);

for (int i=0; i<npaths; i++){
S = S0;
for (int j=0; j<nsteps; j++){
normalRandom(rnorm);
S *= exp((r-0.5*sigma*sigma)*dt + sigma*sqrt(dt)*rnorm[0]);
S *= exp((r-0.5*sigma*sigma)*dt + sigma*sqrt(dt)*rnorm[1]);
}
sumpayoff += max(S-K, 0.0);
}

double callprice = double(sumpayoff)/double(npaths);
cout << "Call Price: " << callprice << endl;

return 0;
}