collatz.cpp

#include <set>
#include <iostream>

template<typename T> size_t collatz(T x) {
  std::set<T> xs;
  size_t n = 0;
  for (;; n++) {
    if (x == 1)
      break;
    if (xs.find(x) != xs.end()) {
      std::cout << "LOOP" << std::endl;
      exit(1);
      return n;
    }
    xs.insert(x);
    if (x % 2 == 0)
      x = x /2;
    else
      x = x * 3 + 1;
  }
  return n;
}

int main(int argc, char** argv) {
  for (size_t i = 1;; i++)
    std::cout << i << ":" << collatz<int32_t>(i) << std::endl;
}