[交流] Euler 工程 第14题：找最长的数列 已有6人参与

%% Which starting number, under one million, produces the longest chain?
%   n = n/2 (even); n = 3*n+1 (odd) till n==1
% like starting from 13, we generate the following sequence (contains 10 terms)
%  13 → 40 → 20 → 10 → 5 → 16 → 8 → 4 → 2 → 1

function result = euler14()
tic;
n = 0;
len = 0;
big = 0;
result = 0;
for i=1:1e6
    n = i;
    len = 0;
    while n~=1
        if mod(n,2)==0
            n = n/2;
        else
            n = n*3+1;
        end
        len = len+1;
    end
    len = len+1; % n==1
   
    if len>big
        big = len;
        result = i;
    end
end
toc;
end

% Elapsed time is 13.644453 seconds.
% ans =
%       837799