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

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mrs_matlab_rookie_thanks 2015-9-22

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编辑： Walter Roberson 2015-9-22

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!

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Thorsten 2015-9-22

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

mrs_matlab_rookie_thanks 2015-9-22

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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

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Answer 1

Varun Pai 2015-9-22

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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);

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Answer 2

Thorsten 2015-9-22

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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.