How can I solve this odd/even loop question (hailstone sequence)?

n = 71
If n is even, divide it by 2 to get n / 2.
If n is odd, multiply it by 3 and add 1 to obtain 3n + 1. 
Repeat process until n = 1.

I need to find out how many steps it takes to reach 1..

thanks!

[Thorsten]

What have you tried so far? Where did you got stuck?

[mrs_matlab_rookie_thanks]

ok, so im really new to matlab, but this is what i tried doing:

n(1,1) = 71;

iterations(1,1) = 0;

ii=1;

while n(1,ii)==1;

      if mod(n(1,ii),2)==1

          (3*n(1,ii))+1;

      else n(1,ii)/2;

        ii=ii+1;

      end

       iterations(1,ii) = iterations(1,ii) + 1; 
  end

Answer 1

[Varun Pai]

I think this is your requiremnt. Please check

num = 71;
count = 0;
while(num~=1)
  count = count+1;
  if(mod(num,2)==0)
      num = num/2;
  else
      num = 3*num + 1;
  end
end
fprintf('count = %d', count);

Answer 2

[Thorsten]

First you can skip the 1, and just write n(ii).

Next you have forgotten to assign the new value, and you have to move the increment of ii outside the else-clause

        if mod(n(ii),2)==1
          n(ii+1) = 3*n(ii)+1;
        else 
          n(ii+1) = n(ii)/2;
        end

        ii=ii+1;

Finally you have to change the while loop condition; while n(ii) == 1 means that the loops only continues if the n is 1, but it should continue if n is NOT 1.

[mrs_matlab_rookie_thanks]

great! thanks for the explanation :)