Cannot understand the detailedly the following code
A.T.Hofkamp
hat at se-162.se.wtb.tue.nl
Wed Apr 9 17:12:49 CEST 2008
On 2008-04-09, reachmsn at hotmail.com <reachmsn at hotmail.com> wrote:
> On Apr 8, 5:45 pm, "A.T.Hofkamp" <h... at se-162.se.wtb.tue.nl> wrote:
> Ok following these instructions one gets
>
> def find_all_paths(graph, start, end, path=[]):
> path= path+ [start]
>
> for node in graph[start]:
>
> find_all_paths(graph, node, end, path)
>
>> First define the input and output parameters/values of the function.
>> (ie what goes in, and what comes out)
>
> Now what will be the output parameters - there is a Return statement.
> Input parameters are graph, vertexes start, node, end and path. Also
> how would you write the terminating and reduction cases after this.
> Actually i'm not clear how to proceed writing this recursive function.
> Thanks!
Don't look at code, don't even think about it (it gives you too much confusing
details).
Instead, have a beer, sit down in a sunny spot, and do mothing for a while.
Think about the function as a (black) box. You don't know what is in it (it is
not important yet). That box is the function (many people prefer to draw a
rectangular shape on a sheet of paper, and consider that to be the function).
What data does the box need to do its work, and what does it produce after
it has done its work?
(suppose you are given the task of 'finding all paths'. What information do you
need to acomplish this task, and what information do you write down as result?)
A simple example of a multiplication task: One needs 2 numbers to do the task,
and the result is another number. Note that at this stage, you don't worry
about HOW you do the task, only WHAT GOES IN AND WHAT COMES OUT.
(actually, HOW depends on INPUT. Multiplication of 2 and 5 can be done
differently from multiplication of
230698762085269459068388639078903870385790368703879038285790 and
5938063786093895682682968390789380834687387689762897. For this reason, deciding
the strategy of solving the problem comes after establishing input and output).
Sincerely,
Albert
PS email will give you shorter response times.
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