Collatz conjecture using only c++ templates

main.cpp

#include <iostream>

template <int N>
struct collatz;

template <>
struct collatz<1> {
    static const int ans = 1;
};

template <int N>
struct collatz_even {
    static const int ans = 1 + collatz<N/2>::ans;
};

template <int N>
struct collatz_odd {
    static const int ans = 1 + collatz<3*N+1>::ans;
};

template <int N, bool is_even>
struct checker;

template <int N>
struct checker<N, true> {
    static const int ans = collatz_even<N>::ans;
};

template <int N>
struct checker<N, false> {
    static const int ans = collatz_odd<N>::ans;
};

template <int N>
struct collatz {
    static const int ans = checker<N, (N%2 == 0)>::ans;
};

int main() {

    std::cout << collatz<50>::ans << '\n';

    return 0;
}