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# binary tree

Posted on 1998-11-29
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i need a code for removing a node from the tree, considerating all cases. function suld be recursive.
very basic c++ - no templates , very close to c language , but with treenode class that holds the tree, and node class
that holds only the data. i hope it's not too much to ask. thank you very much for your help!
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Question by:liorliat
• 9
• 4

Author Comment

Edited text of question
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Author Comment

node class has 3 node pointers - left , right , parent.
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Author Comment

node class has 3 node pointers - left , right , parent.
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Author Comment

node class has 3 node pointers - left , right , parent.
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Accepted Solution

Booth882 earned 100 total points
do you want to remove a node from anywhere or one from the outermost branches (ie one with no Right or Left pointer)?  to remove one from the outermost branches you could say

node * CurrentNode = trunk // trunk is the base node in the tree

while(CurrentNode->Left || CurrentNode->Right)
{
if(CurrentNode->Left)
CurrentNode = CurrentNode->Left;
else
CurrentNode = CurrentNode->Right;
}

if(CurrentNode->ParentNode->Left == CurrentNode)
CurrentNode->ParentNode->Left = 0;
else
CurrentNode->ParentNode->Right = 0;

EraseNode(CurrentNode);

I think this is what you want to do, because to remove a node from an arbitrary location would take the removal of all the nodes it is a parent and grandparent etc to.  you could do that though too.  all it would take would be to take the above algorithm and repeat until the node you want to remove has no branches coming from it, ie

if(RemovalNode->Right == 0 && RemovalNode->Left == 0)

and instead of using the trunk of the whole tree to initialize CurrentNode use the node you want to remove, like this

void RemoveNode(node * RemovalNode)
{
while(RemovalNode->Right != 0 && RemovalNode->Left != 0)
{
node * CurrentNode = RemovalNode;

while(CurrentNode->Left || CurrentNode->Right)
{
if(CurrentNode->Left)
CurrentNode = CurrentNode->Left;
else
CurrentNode = CurrentNode->Right;
}

if(CurrentNode->ParentNode->Left == CurrentNode)
CurrentNode->ParentNode->Left = 0;
else
CurrentNode->ParentNode->Right = 0;

EraseNode(CurrentNode); // however you are doing this,
// possibly delete CurrentNode;?
}
}

that should do it.  let me know if you have any questions.
0

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Expert Comment

hey liorliat?  you still there?...
0

Author Comment

thank you very much for you'r answer.
i'm afraid that it was'nt exactly what i ment. i want to delete an arbitrary node from the tree, and keep the property of a binary tree.
by now, i wrote the  functions to do the next:
1) find the predecessor of a node,by sending the pointer of the node.
2) find the successor.
3) find a node in the tree by getting its data (an integer in my qestion case)
4) find min and max from a node (functions gets the pointer to the node)
all functions returns a pointer to the node found , or NULL .
now,using all this function,and having right left and parent pointer in each node,how do i delete an arbitrary node,keeping the property of a binary tree still?
0

Author Comment

thank you very much for you'r answer.
i'm afraid that it was'nt exactly what i ment. i want to delete an arbitrary node from the tree, and keep the property of a binary tree.
by now, i wrote the  functions to do the next:
1) find the predecessor of a node,by sending the pointer of the node.
2) find the successor.
3) find a node in the tree by getting its data (an integer in my qestion case)
4) find min and max from a node (functions gets the pointer to the node)
all functions returns a pointer to the node found , or NULL .
now,using all this function,and having right left and parent pointer in each node,how do i delete an arbitrary node,keeping the property of a binary tree still?
0

Author Comment

thank you very much for you'r answer.
i'm afraid that it was'nt exactly what i ment. i want to delete an arbitrary node from the tree, and keep the property of a binary tree.
by now, i wrote the  functions to do the next:
1) find the predecessor of a node,by sending the pointer of the node.
2) find the successor.
3) find a node in the tree by getting its data (an integer in my qestion case)
4) find min and max from a node (functions gets the pointer to the node)
all functions returns a pointer to the node found , or NULL .
now,using all this function,and having right left and parent pointer in each node,how do i delete an arbitrary node,keeping the property of a binary tree still?(sorry th bother you again...)    :-)
0

LVL 1

Expert Comment

what do you mean by keep the property of a binary tree?

could you clarify what you mean by 'property'?
0

Author Comment

by saying "keep the property of binary tree" i mean that the tree would still be sorted as a binary tree after the removal of an arbitrary node.
please give me an answer as soon as possible,  i need it  7 hours from now !!!
thanks again.

0

LVL 1

Expert Comment

the second algorithm I showed you would still keep it sorted as a binary tree.  it is necessary to delete all the nodes that spring from the removed node because otherwise you would have no connection to them and their memory would be lost, but after you are done it will still be a binary tree.  give it a try, it works! :)
0

Author Comment

thanks a lot fo your quick response.
you SAVED me!
i'll be talking to you when i'll have another  ?
it probebly wont take long...  :)
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