M-file for producing a random permutation of 1,...,n and then breaking it into disjoint cycles

% M-file for producing a random permutation of 1,...,n and then breaking it into disjoint cycles

n=input('Type n ');

p=randperm(n)

pstart=p; % Just in case you want to be reminded what p was at the end

disp('Now follow the cycles of this permutation')

i=0;

while i i=i+1;
if p(i)>0
v=[];
flag=0; % flag is just to trick
% the computer into entering
% the while loop
first=i;
while (first ~=i) | (flag==0)

% ~= means not equal
% and | means or
flag=1;
r=first;
v=[v r];
first=p(first);
p(r)=0; % The entries in the cycle are changed
% to zero to indicate that they
% have been `used'
end;
disp(v)
end;
end;