colatz.cpp

#include <iostream>
#include <map>
#include <iterator>

#include <math.h>
#include <unistd.h>

using namespace std;

std::map<int, int> Cache;
std::map<int, int>::iterator it;

int calculate_collatz(int num)
{
    int counter = 1;
    unsigned long int curr = num;

    while(true)
    {
        // it = Cache.find(curr);
        // if(it != Cache.end())
        // {
            // counter += Cache.find(curr)->second;
            // return counter;
        // }
        if(curr == 1)
        {
            break; // base case
            counter++;
        }
        if(curr % 2 == 0) // even
        {
            curr = curr / 2;
            counter++;
        }
        else
        {
            curr = 3*curr + 1;
            counter++;
        }
    }
    return counter;
}

int main(int argc, char *argv[])
{
    int count = 0;
    int biggest_num = 0;
    int num = 13;
    while(true)
    {
        int result = calculate_collatz(num);
        Cache.insert(std::make_pair(num, result));
        if(result > count)
        {
            biggest_num = num;
            count = result;
            // cout << "Biggest number: " << biggest_num << " with " << count << " terms" << endl;
        }
        num++;
        // if (num > 50) break;
        if (num > 1000000) break;
    }
    cout << "Biggest number: " << biggest_num << " with " << count << " terms" << endl;
    return 0;
}