how many flips until n heads

coins.cpp

// How many times do you have to flip a coin
// to get n heads?
#include <random>
#include <iostream>

int main() {
    std::random_device rd;
    std::mt19937 gen(rd());
    std::uniform_int_distribution<> dis(0,1);

    long double expected = 0.0L;
    int heads = 0;
    int trials = 0;
    int MAXN = 1e6;
    int HEADS = 2;

    for(int i = 0; i < MAXN; ++i) {
        trials = 0;
        heads = 0;
        while(heads < HEADS) {
            if(dis(gen))
                ++heads;
            else
                heads = 0;
            ++trials;
        }
        std::cout << trials << std::endl;
        expected += (long double)trials;
    }

    std::cout << (long double)(expected/MAXN) << std::endl;

    return 0;
}