## Re: 1st version exercise 3.16 sequence predication problem

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• ... What I means: dead end means It is impossible to further expand the node, that s no possible action If a node can be broken ... further ... According
Message 1 of 3 , Nov 15, 2003
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--- In aima-talk@yahoogroups.com, "Brandon Corfman" <bcorfman@a...>
wrote:
> I'm not sure what you mean by "dead end".
What I means:
"dead end" means "It is impossible to further expand the node, that's
no possible action"

If a node can be broken
> down, into a new center node and two leaves, then at some point, the
> whole process will stop because there are no more operations to be
> performed. (In other words, how can you break down 2 down any
further
> than 1 + 1 in the operations given?)

According the books guide, it is allowed to break down
("expand") "1+1". For example:
1. replace the first "1" in "1+1" state by "(1+1)+1
2. replace the first "1" in "1+1" state by "(1+n)+1
3. replace the first "1" in "1+1" state by "(n+n)+1
4. replace the first "1" in "1+1" state by "(n+1)+1 (One of my
question is "delete this action or not, because this is same as above
item "2")
5. replace the first "1" in "1+1" state by "(1-1)+1
6. replace the first "1" in "1+1" state by "(n-1)+11.
7. replace the first "1" in "1+1" state by "(n-n)+1
7. replace the first "1" in "1+1" state by "(1-n)+1
...
...
...

kind regards/chenyu

>
> I think that you are breaking things down too far. If you have a
tree
> with all 1's or n's at leaf nodes and +,-,/, or * in the internal
> nodes, then the problem seems to indicate that that should be your
> goal condition.
>
> This is speculation, since I haven't worked through the problem
> myself, but these are my initial impressions.
>
> Brandon
>
> --- In aima-talk@yahoogroups.com, "chenyu468" <chenyu468@y...>
wrote:
> > hi everyone,
> > 1. According to the guide, it is necessary to build a binary-tree
for
> > representing the "state". The tree's leaves are "1" or "n" and
> > internal nodes are "+" "-" "*" "/" "exp" operator.
> >
> > 1. I don't know how to check the "dead end" for expression. If
> > no "dead end" check, it seems that only "breadth_first_search" is
> > acceptable. The the speed and space complexity is too high.
> >
> > 2. the "action" set for replacing "1" is 16 (20-4) by deleting "n
> > divide n", "1 divide 1", "1 multiply 1", "exp(1,1)", "
> > for replacing "n" is also 16 for the similar reason.
> > The expanding branch factor is too high (16). How to reduce it?
> >
> > 3. I don't know how to identify the "same state" from different
path
> > for avoiding expanding them. Could you tell me? Or is it possible
to
> > create unique tree everytime, therefore no need to identify them
are
> > the same state or not?
> >
> > Thank you in advance.
> > kind regards/chenyu
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