updown3.m

《精通matlab7》“mastering matlab 7”的代码。

% updown3.m
% up-down algorithm

if ~exist('Nums','var')     % numbers to test
   Nums = 25:50;
end
Counts = zeros(size(Nums)); % preallocate array
N = Nums(1);                % predefine N data type and dimension
count = 0;                  % predefine count data type and dimension

for i=1:length(Nums)
   N = Nums(i);  % number to test
   count = 0;  % iteration count
	while N>1
       if rem(N,2)==0 % even
          N = N/2;
          count = count+1;
       else           % odd
          N = (3*N+1)/2;
          count = count+2;
       end
	end
	Counts(i) = count;
end
%results = [Nums' Counts']