Strange Problem

[ariesthechamp]

I've never run into this problem before. The routine stops in the middle of execution @ the number 113383. If you inspect the code you'll see that the stopping condition in the for loop has clearly not been satified. To be honest, I'm baffled. I even ran the code on my other comp. Same results. My request is: someone paste the code into your IDE (or wherever) and see if the same thing happens.

//#include <ttmath/ttmath.h>
#include <iostream>
#include <conio.h>

#define MAX 1000000
//n = n/2 ( when n is even)
//n = 3n + 1 ( when n is odd)
using namespace std;

int main ()
{
   // Collatz Problem
   // HOTPO = Half or Triple Plus One
   // count = how many HOTPO calculations until HOTPO reaches one
   long HOTPO = 0, count = 0;

   for (int i = 100; i < MAX; i++){
       HOTPO = i;
       count++;
       cout << HOTPO << " --> ";
       do{
           if ( HOTPO % 2 != 0 ){
             HOTPO = (3*HOTPO) + 1;
             count++;
           }
           else{
             HOTPO /= 2;
             count++;
           }
       }while (HOTPO != 1);
       cout << count << endl;
       count = 0;
   }
   return 0;
}

[R0mai]

It doesn't stop, it gets into an infinte loop, since long overflows and value of HOTPO gets negative for 113383.
Changing long to unsigned long works for 113383. I would suggest to use some bignum library if you want to continue (ttmath is a good start :) ).

[ariesthechamp]

*bows* I used unsigned int long etc... thousands of times. Why I didnt use it here is beyond me. Thx ROmai.

PS ttmath is awesome. )

[viliml]

Umm, your algorithm says 4 for 1. Isn't that, like, wrong?

[ariesthechamp]

The routine works perfectly after I changed long HOTPO to unsigned long.
Not sure what you mean vilml, by '4 for 1'. Explain.