Re: trees?

  • From: Alex Hall <mehgcap@xxxxxxxxx>
  • To: programmingblind@xxxxxxxxxxxxx
  • Date: Thu, 21 Oct 2010 07:49:39 -0400

Python, but we are looking ad pseudocode for the moment. The
programming will come in a few days.

On 10/21/10, Homme, James <james.homme@xxxxxxxxxxxx> wrote:
> Hi Alex,
> I forget. What language are you working in?
>
> Thanks.
>
> Jim
>
> Jim Homme,
> Usability Services,
> Phone: 412-544-1810. Skype: jim.homme
> Internal recipients,  Read my accessibility blog. Discuss accessibility
> here. Accessibility Wiki: Breaking news and accessibility advice
>
>
> -----Original Message-----
> From: programmingblind-bounce@xxxxxxxxxxxxx
> [mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of Alex Hall
> Sent: Wednesday, October 20, 2010 6:03 PM
> To: programmingblind@xxxxxxxxxxxxx
> Subject: Re: trees?
>
> That is what the professor said. However, I fail to see how the
> algorithm moves backwards, and other code-specific concepts, and the
> professor only explains in terms of a tree... I will have to meet with
> her Friday if Friday's class does not clear anything up.
>
> On 10/20/10, Hamid Hamraz <hhamraz@xxxxxxxxx> wrote:
>> Hi,
>> The algorithm for the 8-queen problem may do this:
>> First consider each node of the tree as a representation of a state of the
>> board. For example, the root node is representing a chess board with a
>> queen
>> in the cell (1,1), that is the top left cell. Let's say that the algorithm
>> is smart enough not to place the second queen in the same row. next step
>> is
>> to produce the first child node of the root, which represents a chess
>> board
>> with the first queen at (1,1), and the second one, in (2,1). That is a
>> conflict, so the algorithm backtracks to the root and span another child
>> of
>> the root,which is a chess board with the second queen in (2,2). again
>> conflict, and the algorithm should backtrack to the root. It does this
>> until
>> it finds a none-conflicting state for row 2. and then it moves forward to
>> the 3rd row and so on. sometimes the algorithm may need to backtrack more
>> than one level.
>> please note that the algorithm is not allocating memory for the whole
>> tree,
>> it only needs to keep track of the current working state. If you look to
>> what algorithm is doing as a whole, you can conceptualize a very big tree
>> with a 8 to the power of 8 nodes, each of them representing a chess board
>> with 1 to 8 queens placed, each in one row, conflicting or not. The
>> mission
>> of the algorithm is to crawl among the various nodes of the tree until it
>> finds a leaf node without any conflict. that is the 8 queens are placed
>> there in a none-conflicting situation. If the algorithm continues crawling
>> it can find 92 different solutions for the problem, among the huge search
>> space of 8 ^8 states.
>> This may look too much information, but when you understand it then it is
>> easy and it becomes a solid basis for similar problems, that are arising
>> very often in computer sciences.
>> Last but not least, I just wanted to relate the concept of the trees to a
>> solutionof mine. The algorithm at your hand may be different. It may be
>> more
>> heuristical or may be sillier. But the concept of the tree, as a
>> representation of the search space is similar.
>> HTH
>> Hamid
>> ----- Original Message -----
>> From: "Alex Hall" <mehgcap@xxxxxxxxx>
>> To: <programmingblind@xxxxxxxxxxxxx>
>> Sent: Wednesday, October 20, 2010 6:49 PM
>> Subject: Re: trees?
>>
>>
>>>I get the concept, but that does not help me relate what the code is
>>> doing with the tree (where, exactly, it is in the tree, why it stops
>>> at a certain point, where it goes back to...)
>>>
>>> On 10/20/10, Client Services <Operations@xxxxxxxxxxxxxxx> wrote:
>>>> Don't get very caught up in the drawing.
>>>> I think you grasp the concept already.
>>>> A tree with multiple branches and sub branches.
>>>> Create your own picture in your mind.
>>>>
>>>> H.R. Soltani
>>>>
>>>> -----Original Message-----
>>>> From: programmingblind-bounce@xxxxxxxxxxxxx
>>>> [mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of Alex Hall
>>>> Sent: Wednesday, October 20, 2010 10:54 AM
>>>> To: programmingblind@xxxxxxxxxxxxx
>>>> Subject: Re: trees?
>>>>
>>>> In this case, I am talking about a tree os possibilities, where the
>>>> root is where you start and each of the root's children can have 0 or
>>>> more subtrees of their own... You see why this is so hard to represent
>>>> in an accessible way.
>>>>
>>>> On 10/20/10, Phil Vlasak <pcsgames@xxxxxxxxxxx> wrote:
>>>>> Hi Alex,
>>>>> In an architecture plan, a tree is a circle with a dot at the center.
>>>>> The
>>>>> point represents the center of the trunk, and a circle represents the
>>>>> average distance the branches reach out.
>>>>>
>>>>> ----- Original Message -----
>>>>> From: "Alex Hall" <mehgcap@xxxxxxxxx>
>>>>> To: "programmingblind" <programmingblind@xxxxxxxxxxxxx>
>>>>> Sent: Wednesday, October 20, 2010 10:32 AM
>>>>> Subject: trees?
>>>>>
>>>>>
>>>>>> Hi all,
>>>>>> We are doing trees in an algorithms class I am taking. The assignment
>>>>>> coming up is the "n queens" problem, where you have an n by n board
>>>>>> and must place n queens on the board such that no two queens share the
>>>>>> same row, column, or diagonal line. To "help" explain this, the
>>>>>> professor is using a tree on the board. I am completely confused! She
>>>>>> says I do not need to think of it in terms of trees, yet the only way
>>>>>> she explains it is in tree terms, so I am not sure what she is talking
>>>>>> about. Of course I know about trees, but when she tries to explain how
>>>>>> the code we are looking at relates to the tree in terms of what the
>>>>>> code is supposed to do, I haven't a clue as to what she is trying to
>>>>>> say. Does anyone have any thoughts on how to represent trees, whether
>>>>>> in braille or speech, or a good notation/substitute for a tree? TIA.
>>>>>>
>>>>>> --
>>>>>> Have a great day,
>>>>>> Alex (msg sent from GMail website)
>>>>>> mehgcap@xxxxxxxxx; http://www.facebook.com/mehgcap
>>>>>> __________
>>>>>> View the list's information and change your settings at
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>>>>>
>>>>>
>>>>>
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>>>>
>>>>
>>>> --
>>>> Have a great day,
>>>> Alex (msg sent from GMail website)
>>>> mehgcap@xxxxxxxxx; http://www.facebook.com/mehgcap
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>>>
>>>
>>> --
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>
>
> --
> Have a great day,
> Alex (msg sent from GMail website)
> mehgcap@xxxxxxxxx; http://www.facebook.com/mehgcap
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-- 
Have a great day,
Alex (msg sent from GMail website)
mehgcap@xxxxxxxxx; http://www.facebook.com/mehgcap
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