Pretty urgent- I need a class member function to do a level by level traversal of a binary search tree. All the books I have give recursive code for in-, pre- and post-order traversal, but this seems rather different (and is iterative) I found a pseudocode version of a level-order graph traversal, but it leaves out the problem I am having- how to move from the node you are on to the adjacent one and so on down the tree. The pseudocode function I have is:

Assume a binary tree with n levels

Each node contains a boolean variable "visited"

Binary class has a member function to mark visited TRUE

Using a basic queue, which has a NotEmpty function that returns TRUE/FALSE.

Start at the root node

Enqueue the value in the root node

while (Queue not empty)

{

Dequeue first value

for (each unvisited node adjacent to the the current node)

{

Mark node as visited

Enqueue value in current node

} // end for

} // end while

That for loop condition is just a bit vague!! Like I said, my problem is how to move thru the tree. I could hard code for a set number of levels, but obviously this is not acceptable. So I need a fairly specific function, although you are free to use whatever (descriptive) names you want for any member/helper functions or pointers needed. I just need to be able to see what the function would do. I suspect though that it mainly requires pointer manipulations. I have the code for the bst, queue, etc, just need this one function...

Assume a binary tree with n levels

Each node contains a boolean variable "visited"

Binary class has a member function to mark visited TRUE

Using a basic queue, which has a NotEmpty function that returns TRUE/FALSE.

Start at the root node

Enqueue the value in the root node

while (Queue not empty)

{

Dequeue first value

for (each unvisited node adjacent to the the current node)

{

Mark node as visited

Enqueue value in current node

} // end for

} // end while

That for loop condition is just a bit vague!! Like I said, my problem is how to move thru the tree. I could hard code for a set number of levels, but obviously this is not acceptable. So I need a fairly specific function, although you are free to use whatever (descriptive) names you want for any member/helper functions or pointers needed. I just need to be able to see what the function would do. I suspect though that it mainly requires pointer manipulations. I have the code for the bst, queue, etc, just need this one function...

struct TNode {

...

TNode* pLeft;

TNode* pRight;

} ...

it possible only using some additional storage... like that...

You creating array of size equal to Tree height (for binary search tree like RB-tree or AVL-Tree its not bigger than 2*log2(TreeSize). Each element of the array is queue of the node pointers. Now You doing preorder on the tree counting current level number and inqueuing node pointer into queue with index equal to current level... than you can walk through resulting data-structure :) any way You want.

Note: Working (almoust commercial) example of AVL-Tree implementetion is at "http:\\come.to\okthinks" (Natlib Class Library)...

preorder have to be realized like that:

// can be static member of the function or member of the

// class or even one of the params of the recursion

//------------------------

size_t nLevel = 0;

// size is the height of the tree. If You going to

// use Natlib the vector is self growing

//------------------------

TVectorOf< TVectorOf<TNode*> > aa_Levels[...];

//------------------------

void CollectByLevels(const TNode* pc_Node)

{

aaLevels[nLevel].Insert(pc

++nLevel;

if (pc_Node->pLeft) Preorder(pc_Node->pLeft);

if (pc_Node->pRight) Preorder(pc_Node->pRight);

--nLevel;

} /*CollectByLevels(const TNode*)*/

Preorder(Tree.pRoot);

or

//------------------------

void CollectByLevels(const TNode* pc_Node, size_t nLevel)

{

aaLevels[nLevel].Insert(pc

if (pc_Node->pLeft) Preorder(pc_Node->pLeft, nLevel + 1);

if (pc_Node->pRight) Preorder(pc_Node->pRight, nLevel + 1);

} /*CollectByLevels(const TNode*, size_t)*/

CollectByLevels(Tree.pRoot

Unethical behavior, either by the client asking the question or the expert answering, is grounds for removal from EE.

I can. If you would like HELP, I will ASSIST you in meeting your assignment. I will not give you the answer.

what u have given ac lagorithm is breadth first search for graph (not binary search tree).

If u want it just for binary search tree

instead for each unvisited node

just say for leftchild and for rightchild.if they exist.

for queue implementation why not use linked list.

About efficiency of the solution...

the execution time of it is O(TreeSize)

the memory requirements is about sizeof(void*) * TreeSize + C, where C is size of vector implementation;

I'm not sure there are any reasons to extend size of the Node structure to hold additional information like Is Visited or Pointer To Sibling Node... it can take even more space... and cleaning of these fields an take some time ... imagine that You need to perform iteration more than once... More than that if You already have implementation of the tree from 3d parties :) and don't want to go and change it (or unable to do that) what can be Your idea?

>>I'm not sure there are any reasons to extend size of the Node

>> structure to hold additional information like IsVisited

>> or PointerToSiblingNode

that's not part of the algrithm. You don't need the IsVisited to get this accomplished, that is requested in the question probably as a way to test that the algrithm is working. You definitly don't need a pointer to the subling node in a binary tree. There are trees where that is good to have, but not for this task or for a binary tree.

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