I am sorry , and thanks for your friendliness . I have change my source code for more meaningful variable name and more comments follow the instructions John has writen . I think that is useful for you to look my code .
And this time I put the code in the attachment . Indeed , I write that in the Eclipse Pydev , I don't know why it lose its idention in the mailing list . Also , I forget an example for the question , and I compensate for it : Given the integer 2 for instance : what we exapct from the algorithm is a list of 0 or 1 , for this instance it is 1 1 0 0 . We can take it as a ring , and fetch any continuous 2 numbers from it , finally get four combinations : 11 , 10 , 00 , 01 and they are 3 , 2 , 0 , 1 . I hope this time it is clear for all to understand what problem confront me . And again I am sorry for the trouble , thanks for you again ! Best Regard Bo Yang -- http://mail.python.org/mailman/listinfo/python-list