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Re: Challenge #6 for programming nerds

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iMightBeLying is not online. iMightBeLying
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Joined: 04 Sep 2014
Total Posts: 144
06 Mar 2015 03:20 PM
Good afternoon OT and welcome to Friday. You may be looking forward to the weekend and RDC, but I'm looking forward to stress testing your brain. Today's challenge is....... Sorting Lists!

But first, a little information...

A Node object looks like this. It holds a value and a reference to the nodes before and after it.
Node
{
int value;
Node previous;
Node next;
}

A Doubly Linked List is a data structure comprised of Node objects. It is similar to an array but it is not a fixed size, so it can easily grow when more Nodes are added to it or removed. A bare bones DLinkedList looks like this. It holds a reference to the first Node in the list, the last Node in the list, and a running total of how many Nodes are in the list.
DLinkedList
{
Node head;
Node tail;
int numObjects;
}

When a new Node is added to the list, it is added to the Tail Node's next value, and that new Node becomes the new tail.
For example:
void addNode ( int aNodeValue )
{
Node aSampleNode = new Node ( aNodeValue ); //create the new node
aSampleNode.previous = list.tail; //keep a reference to the old tail
list.tail.next = aSampleNode; //add the new node to the list
list.tail = aSampleNode; //update the list so the tail is now the newest node
}

Removing a Node is just as easy. All you have to do is rewire the references to splice Nodes out of the list.
For example:
void removeNode ( Node outNode )
{
Node previousNode = outNode.previous;
Node nextNode = outNode.next;
previousNode.next = nextNode; //rewire the previous reference to point past the node we're removing
nextNode.previous = previousNode; //rewire the next reference to point past the node we're removing

//now there are no references in the list to the node we're removing
//clean up the node before deleting it
outNode.previous = null;
outNode.next = null;
outNode.delete( );
}


Okay, now you know everything you need to know about Doubly Linked Lists. So, now onto the real challenge.
imagine that I have an unsorted DLinkedList filled with 0s, 1s, and 2s.

Write a function that will sort the DLinkedList so that all the 0s are first, the 1s are in the middle, and the 2s come last.
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Dreamlike is not online. Dreamlike
Joined: 29 Feb 2012
Total Posts: 16147
06 Mar 2015 03:20 PM
7
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uberpwner123 is not online. uberpwner123
Joined: 04 Jun 2010
Total Posts: 7791
06 Mar 2015 03:21 PM
I'll...
do this later.

+2.2k posts
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rockhopper99 is not online. rockhopper99
Joined: 18 May 2008
Total Posts: 5645
06 Mar 2015 03:22 PM
you come to the wrong place with this
we are the misfits


-2baked4siggy
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DrForce is not online. DrForce
Joined: 29 Sep 2013
Total Posts: 35008
06 Mar 2015 03:23 PM
Wait
How does a horse know so much scripting
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iMightBeLying is not online. iMightBeLying
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Total Posts: 144
06 Mar 2015 03:25 PM
@rockhopper99

I come here almost every day with challenges and brain teasers. This week it has been programming challenges. Last week it was math and process challenges.
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Dreamlike is not online. Dreamlike
Joined: 29 Feb 2012
Total Posts: 16147
06 Mar 2015 03:25 PM
Do logic next week
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DrForce is not online. DrForce
Joined: 29 Sep 2013
Total Posts: 35008
06 Mar 2015 03:26 PM
Wait what's going to be next week's thing then?
Because well I hope it's somethin good, my birthday is on monday xd
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AverageWhiteGirlOfOT is not online. AverageWhiteGirlOfOT
Joined: 15 Nov 2014
Total Posts: 171
06 Mar 2015 03:26 PM
sometimes i wish i could own all the makeup in the world! haha!
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iMightBeLying is not online. iMightBeLying
Forum Moderator
Joined: 04 Sep 2014
Total Posts: 144
06 Mar 2015 03:27 PM
@DrForce

send me a PM, you can help me decide next week's challenge theme
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DrForce is not online. DrForce
Joined: 29 Sep 2013
Total Posts: 35008
06 Mar 2015 03:28 PM
Alright.
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rockhopper99 is not online. rockhopper99
Joined: 18 May 2008
Total Posts: 5645
06 Mar 2015 03:29 PM
do logic next week [2]

-2baked4siggy
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iMightBeLying is not online. iMightBeLying
Forum Moderator
Joined: 04 Sep 2014
Total Posts: 144
06 Mar 2015 03:29 PM
@rockhopper99

Is your birthday on Monday?
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uberpwner123 is not online. uberpwner123
Joined: 04 Jun 2010
Total Posts: 7791
06 Mar 2015 03:30 PM
philosophy or logic would be nice
please don't use the concept of infinity either

+2.2k posts
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rockhopper99 is not online. rockhopper99
Joined: 18 May 2008
Total Posts: 5645
06 Mar 2015 03:30 PM
@iMightBeLying
May 6th 1998

-2baked4siggy
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iMightBeLying is not online. iMightBeLying
Forum Moderator
Joined: 04 Sep 2014
Total Posts: 144
06 Mar 2015 03:31 PM
@everyone

Send me your suggestions for topics in a PM, don't post them here.

Right now, there's a DLinkedList that needs sorting.
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OTRainbowDash5000 is not online. OTRainbowDash5000
Joined: 29 Jul 2013
Total Posts: 14883
06 Mar 2015 03:39 PM
Gonna start working on this now.

Should be fun since Lua doesnt have a native implementation of doubly linked lists, so Ill have to implement that myself.


crush, kill, destroy, swag -roblox skin plugin dev
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iMightBeLying is not online. iMightBeLying
Forum Moderator
Joined: 04 Sep 2014
Total Posts: 144
06 Mar 2015 04:06 PM
@RainbowDash

if you are implementing DLinkedLists yourself, there are a few special cases you should account for.

When removing a Node, check if that node is the list's head or tail, and make sure that you update the list appropriately once that node is removed.
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DrForce is not online. DrForce
Joined: 29 Sep 2013
Total Posts: 35008
06 Mar 2015 04:09 PM
I heard my high school has a scripting class like with machines so I'll probably learn it sometime.
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NeneAnegasaki is not online. NeneAnegasaki
Joined: 16 Feb 2015
Total Posts: 594
06 Mar 2015 04:12 PM
Is there any practical use to this?
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iMightBeLying is not online. iMightBeLying
Forum Moderator
Joined: 04 Sep 2014
Total Posts: 144
06 Mar 2015 04:14 PM
@Nene

What are you asking? Is there a practical use for doubly linked lists? Or for sorting lists?
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NeneAnegasaki is not online. NeneAnegasaki
Joined: 16 Feb 2015
Total Posts: 594
06 Mar 2015 04:20 PM
@iMight

I guess for sorting double-linked lists.
I've never seen anyone do this before.

I think I attempted something similar when trying to sort through nodes that represented a Huffman coding. But I don't think that's exactly what you're doing, and that was a pain in a behind.
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MrPhelps is online. MrPhelps
Joined: 27 Feb 2010
Total Posts: 27982
06 Mar 2015 04:26 PM
Why can't we have an easy challenge like building a sentient snowman?






~The OT Snowman~
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Joe11Joe99 is not online. Joe11Joe99
Joined: 22 May 2011
Total Posts: 34458
06 Mar 2015 04:27 PM
tl;dr

all i know is that this is about lists

professional thinker
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iMightBeLying is not online. iMightBeLying
Forum Moderator
Joined: 04 Sep 2014
Total Posts: 144
06 Mar 2015 04:36 PM
@Nene

Why is the data scrambled if I wanted it sorted in the first place? Shouldn't the data be sorted the moment a new node is added? These are valid points.

But, all the arguments for having a sorted array of data apply to having a sorted list. Mostly, it is for easier value look up.

A Node might have more data than just a value. It might also have a bunch of strings and also a timestamp that it was added. For games, it might be bullets that you have fired that are still flying around. Being able to easily sort through a list of an unknown size is very important.

And it is always a cost-benefit analysis you have to run for each case. Is it faster to sort the data and then quickly look up the values you want? Or is it passable to search for each of the values in the unsorted set? Some data sets are small enough that sorting doesn't make sense.
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