collatz.cpp

#include <iostream>

using namespace std;

#define M 3;

int main() {
  int step = 0;
  uint64_t n = 2;
  uint64_t term = 2;
  uint64_t stepsRecord = 0;
  uint64_t termRecord = 0;
  uint64_t maxSafeTerm = 0xffffffffffffffff / 3;
  bool isTermRecord = false;

  while (true) {
    step++;
    if (term % 2 == 0) {
      // The term is even so divide it by 2.
      term /= 2;
      if (term == 1) {
        // The sequence has collapsed to 1.
        if (step > stepsRecord) {
          // New record!
          stepsRecord = step;
          cout << "Step record " << n << ',' << step << endl;
        }
        if (isTermRecord) {
          // New record!
          cout << "Term record " << n << ',' << termRecord << endl;
        }
        // Move on to the next N.
        n++;
        term = n;
        step = 0;
        isTermRecord = false;
      }
    } else {
      if (term > maxSafeTerm) break;
      // The term is odd so do the m.n + 1 calculation.
      term = term * 3 + 1;
      if (term > termRecord) {
        // New record - but check for overflow first.
        // if (term > Number.MAX_SAFE_INTEGER) {
        //   throw new Error('Overflow');
        // }
        termRecord = term;
        isTermRecord = true;
      }
    }
  }
  cout << "Stopped at " << n;
  cout << " with term " << term;
  cout << " on step " << step << endl;
  return 0;
}