I'm coding a binary search tree and I'm having a little trouble finding a way to delete node effectively.
I have this code :
struct node* deleteNode(int i, struct node *N)
{
if (N==NULL)
{
return NULL;
}
else if (i<N->value)
{
N->size--;
N->lChild=deleteNode(i,N->lChild);
}
else if (i>N->value)
{
N->size--;
N->rChild=deleteNode(i,N->rChild);
}
else if (N->lChild==NULL)
{
return N->rChild;
}
else if (N->rChild==NULL)
{
return N->lChild;
}
else
{
N->size--;
N->value=findMin(N->rChild);
N->rChild=deleteNode(N->value,N->rChild);
}
return N;
}
And N is a node structure which have 5 fields : value, lChild, rChild, size, height.
In fact what I'm doing here is to make the tree not to point toward the node that I want to delete but when I'm trying to put something like :
else if (N->rChild==NULL)
{
free(N);
N=NULL;
return N->lChild;
}
Or every similar looking code, it doesn't work. Can someone point me in the right direction please?
Thank you.
First of all you're saying N=NULL and then calling N->lchild N is null and pointing to nothing so how do you expect to get the lchild value?
Since this is homework I won't give a direct answer but hints.
To delete the node, check if it has children, if it doesnt free it and remove references to it such as the parents child ptr.
If it has 1 child swap the ptr that points to the node you want to delete with the child and free the node. The same applies if you also have 2 children.
Related
Now, I understand that code below works only for root and its children, but I don't know how to expand it. Every node must have children before passing on "grandchildren". Thank you.
void insert_node(IndexTree **root, Node *node) {
IndexTree *temp = (IndexTree*)malloc(sizeof(IndexTree));
memcpy(&temp->value.cs, node, sizeof(Node));
temp->left = NULL;
temp->right = NULL;
temp->tip=1;
if ((*root) == NULL) {
*root = temp;
(*root)->left = NULL;
(*root)->right = NULL;
}
else {
while (1) {
if ((*root)->right == NULL) {
(*root)->right = temp;
break;
}
else if ((*root)->left == NULL) {
(*root)->left = temp;
break;
}
}
}
Use recursive functions.
Trees are recursive data types (https://en.wikipedia.org/wiki/Recursive_data_type). In them, every node is the root of its own tree. Trying to work with them using nested ifs and whiles is simply going to limit you on the depth of the tree.
Consider the following function: void print_tree(IndexTree* root).
An implementation that goes over all values of the trees does the following:
void print_tree(IndexTree* root)
{
if (root == NULL) return; // do NOT try to display a non-existent tree
print_tree(root->right);
printf("%d\n", root->tip);
print_tree(root->left);
}
The function calls itself, which is a perfectly legal move, in order to ensure that you can parse an (almost) arbitrarily deep tree. Beware, however, of infinite recursion! If your tree has cycles (and is therefore not a tree), or if you forget to include an exit condition, you will get an error called... a Stack Overflow! Your program will effectively try to add infinite function calls on the stack, which your OS will almost certainly dislike.
As for inserting, the solution itself is similar to that of printing the tree:
void insert_value(IndexTree* root, int v)
{
if (v > root->tip) {
if (root->right != NULL) {
insert_value(root->right, v);
} else {
// create node at root->right
}
} else {
// same as above except with root->left
}
}
It may be an interesting programming question to create a Complete Binary Tree using linked representation. Here Linked mean a non-array representation where left and right pointers(or references) are used to refer left and right children respectively. How to write an insert function that always adds a new node in the last level and at the leftmost available position?
To create a linked complete binary tree, we need to keep track of the nodes in a level order fashion such that the next node to be inserted lies in the leftmost position. A queue data structure can be used to keep track of the inserted nodes.
Following are steps to insert a new node in Complete Binary Tree. (Right sckewed)
1. If the tree is empty, initialize the root with new node.
2. Else, get the front node of the queue.
……. if the right child of this front node doesn’t exist, set the right child as the new node. //as per your case
…….else If the left child of this front node doesn’t exist, set the left child as the new node.
3. If the front node has both the left child and right child, Dequeue() it.
4. Enqueue() the new node.
I have tried everything to figure out what is wrong with my code. I tried to search for the problem. I tried to redo the code. I even tried to simulate the code several times on a piece of paper and It should work fine. But it's not. So far the code works when I input a root as 5, then add another node for example 8, then add another node 9, then add another node 6. But when I try to add another node for example 3. When I try to display all the nodes, the Node 6 and 9 are gone. But the node 3 was added. Any help would be appreciated.
bool addrec(nd *root,nd *tp,nd *tr,nd *data)//FIX ADDING
{
nd temp;
temp=malloc(sizeof(NODE));
temp->bkNumber=(*data)->bkNumber;
strcpy(temp->bkTitle, (*data)->bkTitle);
strcpy(temp->bkAuthor, (*data)->bkAuthor);
temp->bkCopyright=(*data)->bkCopyright;
temp->left=NULL;
temp->right=NULL;
bool added=false;
if(*root==NULL)
{
*root=temp;
added=true;
}
else
{
*tp=*root;
while(*tp!=NULL)
{
*tr=*tp;
if((*tp)->bkNumber>=(*data)->bkNumber)
*tp=(*tp)->left;
else
*tp=(*tp)->right;
}
if((*tr)->bkNumber>=(*data)->bkNumber)
{
(*tr)->left=temp;
}
else
{
(*tr)->right=temp;
}
added=true;
if((*tr)->right==NULL)//House Keeping To Make Sure the pointers of the new node is pointing to NULL
{
*tr=(*tr)->left;
(*tr)->left=NULL;
(*tr)->right=NULL;
}
else
{
*tr=(*tr)->right;
(*tr)->left=NULL;
(*tr)->right=NULL;
}
}
data=NULL;
temp=NULL;
*tr=NULL;
*tp=NULL;
return added;
}
I've been trying to implement a function in C that deletes a node in a binary tree that should (theoretically) take care of three all cases, i.e.:
Node is a leaf
Node has one child
Node has two children
Is there a way to handle the whole deletion function without checking separately each case? As a commenter below noted I do check for a lot of cases and perhaps the whole problem can be addressed recursively by checking for one fundamental case.
I'm particularly interested in the case where I delete a node within the tree that has a parent and itself is a parent of two children nodes.
Both answers below have been useful but I don't think they address the problem in its entirety.
Here's what I have:
typedef struct Node
{
int key;
int data;
struct Node *left;
struct Node *right;
struct Node *parent;
} Node;
/* functions that take care of inserting and finding a node and also traversing and freeing the tree */
...
void delete(Node *root, int key)
{
Node *target = find(root, key); // find will return the node to be deleted
Node *parent = target->parent; // parent of node to be deleted
// no children
if (target->left == NULL && target->right == NULL)
{
// is it a right child
if (target->key > parent->key)
parent->right = NULL;
// must be a left child
else
parent->left = NULL;
free(target);
}
// one child
else if ((target->left == NULL && target->right != NULL) || (target->left != NULL && target->right == NULL))
{
// here we swap the target and the child of that target, then delete the target
Node *child = (target->left == NULL) ? target->right : target->left;
child->parent = parent;
if (parent->left == target) parent->left = child;
else if (parent->right == target) parent->right = child;
free(target);
}
// two children
else
{
// find the largest node in the left subtree, this will be the node
// that will take the place of the node to be deleted
Node *toBeRepl = max(target->left);
// assign the data of the second largest node
target->key = toBeRepl->key;
target->data = toBeRepl->data;
// if new node immediately to the left of target
if (toBeRepl == target->left)
{
target->left = toBeRepl->left;
Node *newLeft = target->left;
if (newLeft != NULL) newLeft->parent = target;
}
else
{
delete(target->left, toBeRepl->key);
// Node *replParent = toBeRepl->parent;
// replParent->right = NULL;
}
}
I would greatly appreciate your feedback.
edit: Just to clarify, I'm trying to delete a particular node without touching its subtrees (if there are any). They should remain intact (which I've handled by swapping the values of the node to be deleted and (depending on the case) one of the nodes of its substrees).
edit: I've used as a reference the following wikipedia article:
http://en.wikipedia.org/wiki/Binary_search_tree#Deletion
Which is where I got the idea for swapping the nodes values in case of two children, particularly the quote:
Call the node to be deleted N. Do not delete N. Instead, choose either
its in-order successor node or its in-order predecessor node, R.
Replace the value of N with the value of R, then delete R.
There is some interesting code in C++ there for the above case, however I'm not sure how exactly the swap happens:
else //2 children
{
temp = ptr->RightChild;
Node<T> *parent = nullptr;
while(temp->LeftChild!=nullptr)
{
parent = temp;
temp = temp->LeftChild;
}
ptr->data = temp->data;
if (parent!=nullptr)
Delete(temp,temp->data);
else
Delete(ptr->rightChild,ptr->RightChild->data);
}
Could somebody please explain what's going on in that section? I'm assuming that the recursion is of a similar approach as to the users comments' here.
I don't see any "inelegance" in the code, such formatting and commented code is hard to come by. But yes, you could reduce the if-else constructs in your delete function to just one case. If you look at the most abstract idea of what deletion is doing you'll notice all the cases basically boil down to just the last case (of deleting a node with two children).
You'll just have to add a few lines in it. Like after toBeRepl = max(left-sub-tree), check if it's NULL and if it is then toBeRepl = min(right-sub-tree).
So, Case 1 (No children): Assuming your max() method is correctly implemented, it'll return NULL as the rightmost element on the left sub-tree, so will min() on the right sub-tree. Replace your target with the toBeRepl, and you'll have deleted your node.
Case 2 (One child): If max() does return NULL, min() won't, or vice-versa. So you'll have a non-NULL toBeRepl. Again replace your target with this new toBeRepl, and you're done.
Case 3 (Two children): Same as Case 2, only you can be sure max() won't return NULL.
Therefore your entire delete() function would boil down to just the last else statement (with a few changes). Something on the lines of:
Node *toBeRepl = max(target->left);
if toBeRepl is NULL
{
toBeRepl = min(target->right);
}
if toBeRepl is not NULL
{
target->key = tobeRepl->key;
target->data = toBeRepl->data;
deallocate(toBeRepl); // deallocate would be a free(ptr) followed by setting ptr to NULL
}
else
{
deallocate(target);
}
I would do it using recursion, assuming that you have null at the end of your tree, finding null would be the 'go back' or return condition.
One possible algorithm would be:
Node* delete(Node *aNode){
if(aNode->right != NULL)
delete(aNode->right);
if(aNode->left != NULL)
delete(aNode->left);
//Here you're sure that the actual node is the last one
//So free it!
free(aNode);
//and, for the father to know that you're now empty, must return null
return NULL;
}
It has some bugs, for sure, but is the main idea.
This implementation is dfs like.
Hope this helps.
[EDIT] Node *aNode fixed. Forgot the star, my bad.
I finished this a long time ago and I thought it would be good to add a sample answer for people coming here with the same problem (considering the 400+ views this question has accumulated):
/* two children */
else
{
/* find the largest node in the left subtree (the source), this will be the node
* that will take the place of the node to be deleted */
Node* source = max(target->left);
/* assign the data of that node to the one we originally intended to delete */
target->key = source->key;
target->data = source->data;
/* delete the source */
delete(target->left, source->key);
}
Wikipedia has an excellent article that inspired this code.
I wanna make pop function to delete the node and subtree of the node. Here is my code
void pop(struct data *node,int num)
{
if(node)
{
if(node->num==num)
{
pop(node->left,num);
pop(node->right,num);
free(node);
node=NULL;
}
else
{
if(num> node->num)
pop(node->right,num);
else if (num< node->num)
pop(node->left,num);
}
}
}
void pre(struct data *node)
{
if(node)
{
printf("%d ",node->num);
pre(node->left);
pre(node->right);
}
}
void main()
{
push(&root,37);
push(&root,20);
push(&root,45);
push(&root,5);
push(&root,15);
push(&root,40);
push(&root,50);
pre(root);
pop(root,5);
pre(root);
getchar();
}
Pre function works well before I use pop. But after I used the pop function, it's break. Could anyone knows where's the mistake?
In pop, you're doing: node=NULL; -- but this only affects the copy of the pointer that was passed to the function, not the pointer in the original tree. Your tree retains the pointer to the data you've now freed. The next time you do much with the tree, you try to dereference that pointer, and things fall down and go boom (at least you hope they do -- even worse, sometimes they might seem to work).
One way to fix this is to pass a double pointer to pop:
void pop(struct data **node, int num) {
if ((*node)->num == num)
// ...
free(*node);
*node = NULL;
}
}
Now you're changing the pointer in the tree instead of changing the copy of it your function received.
This still won't work quite right though -- you're depending on pop(child, num); to destroy the sub-trees of the current node, but unless their num is set to the same value, they won't delete anything, just travel down the tree looking for a node with a matching num.
You probably want one function to walk the tree finding the node you care about, then a second one that walks the tree starting from a designated node, and (unconditionally) destroys that node and its sub-trees.
Well your pop function should be like this:
struct data* pop(struct data *node,int num)
{
struct data* temp=null;
if(node)
{
if(node->num==num)
{
if(node->left)
pop(node->left,node->left->num);
if(node->right)
pop(node->right,node->right->num);
free(node);
}
else
{
if(num> node->num)
temp=pop(node->right,num);
else if (num< node->num)
temp=pop(node->left,num);
if(node->right==temp)
node->right=null;
else if(node->left==temp)
node->left=null;
return temp;
}
}
return node;
}
This will work as far as you have the logic to nullify the root of the tree from where it is being called, if the desired node tuned out to be root of the tree.
I kinda have to put my previous C questions on hold cause this one is more important now...
I have already coded the insert and delete functions on my binary search tree but the delete function is incomplete. There's a couple of things I need help in...
1) Is my insert function good or can it be improved somehow?
2) My delete function lacks the deletion of a node with both the left and right childs. I've searched a lot in the past few hours but couldn't find a proper way to do it.
2.a) How should I delete a node with 2 child nodes?
2.b) As in the first question, is the delete function good or can it be improved? This one I know it can because I'm repeating lots of code in those ifs but I don't see how can I improve it, I need help on that too.
typedef struct sClientProfile *ClientProfile;
typedef struct sClientTree *ClientTree;
typedef struct sClientProfile {
char *clientName;
int clientAge;
int clientNIF;
} nClientProfile;
typedef struct sClientTree {
ClientProfile clientProfile;
char *clientName;
ClientTree leftTree;
ClientTree rightTree;
} nClientTree;
void addClientToTree(ClientTree *cTree, ClientProfile cProfile) {
if(!*cTree) {
ClientTree new = (ClientTree)malloc(sizeof(nClientTree));
if(!new) {
perror("malloc");
}
new->clientName = strdup(cProfile->clientName);
new->clientProfile = cProfile;
new->leftTree = NULL;
new->rightTree = NULL;
*cTree = new;
} else {
if(strcmp((*cTree)->clientName, cProfile->clientName) > 0) {
addClientToTree(&(*cTree)->leftTree, cProfile);
} else {
addClientToTree(&(*cTree)->rightTree, cProfile);
}
}
}
void deleteClientFromTree(ClientTree *cTree, char *cName) {
if(!cTree) return;
int nCompare = strcmp((*cTree)->clientName, cName);
if(nCompare > 0) {
deleteClientFromTree(&(*cTree)->leftTree, cName);
} else if(nCompare < 0) {
deleteClientFromTree(&(*cTree)->rightTree, cName);
} else {
if(!(*cTree)->leftTree && !(*cTree)->rightTree) {
ClientTree cliPtr = *cTree;
free(cliPtr->clientProfile);
free(cliPtr);
cliPtr->clientProfile = NULL;
cliPtr = NULL;
*cTree = NULL;
} else if(!(*cTree)->leftTree) {
ClientTree cliPtr = *cTree;
free(cliPtr->clientProfile);
free(cliPtr);
cliPtr->clientProfile = NULL;
*cTree = (*cTree)->rightTree;
} else if(!(*cTree)->rightTree) {
ClientTree cliPtr = *cTree;
free(cliPtr->clientProfile);
free(cliPtr);
cliPtr->clientProfile = NULL;
*cTree = (*cTree)->leftTree;
} else {
// MISSING DELETE CASE
}
}
}
You'll probably notice but let me just make 2 remarks:
This tree uses strings instead of the normal int representation. That's why I use strcmp() all the way, I think I'm using it right.
I'm not using recursion, I rather pass the pointer (of a structure pointer in this case) and work with that. It looks more clean somehow and in the future I want to return a success value if a node was deleted.
UPDATE BELOW:
I've already did my iterative version of the delete function but I don't like some things about it, maybe they can be improved (or not) but I can't see how. I've also tried to code the case it was missing, deleting a node with 2 childs, but it's not working as it should...
I've commented the whole code where I think the code can be improved and where's the problem. I've also named those problems as A, B (there's no B anymore), C and D so we can reference to them easily.
bool deleteClientFromTree(ClientTree *cTree, char *cName) {
if(!cTree) return FALSE;
ClientTree currPtr = *cTree;
ClientTree prevPtr = NULL;
int nCompare;
while(currPtr) {
nCompare = strcmp(currPtr->clientName, cName);
if(nCompare > 0) {
prevPtr = currPtr;
currPtr = currPtr->leftTree;
} else if(nCompare < 0) {
prevPtr = currPtr;
currPtr = currPtr->rightTree;
} else {
/*
* A)
*
* The following cases have 3 lines in common, the free()
* calls and return statement. Is there anyway to improve
* this code and make it more compact?
*
* Of course, the printf's are to be removed...
*/
if(!prevPtr && !currPtr->leftTree && !currPtr->rightTree) {
printf("CASE #1\n");
*cTree = NULL;
free(currPtr->clientProfile);
free(currPtr);
return TRUE;
} else if(!currPtr->leftTree || !currPtr->rightTree) {
printf("CASE #2\n");
if(prevPtr->leftTree == currPtr) {
prevPtr->leftTree = currPtr->rightTree;
} else {
prevPtr->rightTree = currPtr->leftTree;
}
free(currPtr->clientProfile);
free(currPtr);
return TRUE;
} else {
printf("CASE #3\n");
ClientTree tempPtr = currPtr->rightTree;
while(tempPtr->leftTree) {
tempPtr = tempPtr->leftTree;
}
/*
* C)
*
* This has a big problem...
*
* If you take a look at the ClientProfile structure,
* in the first post, you'll see two ints
* (clientNIF/clientAge) and one char* (clientName).
*
* The problem is that the following code line is only
* copying the integer data, not the string. For some
* reason, the string remains the old one.
*
* I tried to use strdup() directly on clientName like:
* currPtr->clientProfile->clientName = strdup(tempPtr->clientProfile->clientName);
* but it still doesn't work.
*
* Why everything is being copied but the strings?
*/
currPtr->clientProfile = tempPtr->clientProfile;
/*
* D)
*
* Is there anyway to not call the function itself
* and make the while loop once again and delete the
* corresponding leaf?
*/
return deleteClientFromTree(&currPtr->rightTree, tempPtr->clientProfile->clientName);
}
}
}
return FALSE;
}
When you delete a node, you have to do something about its children.
If there are no children - no problem. You just remove the node.
If there a left child, also no problem; you remove the node and move its left child into its place.
Same for the right child; just move the child into the place of the deleted node.
The problem comes when you want to delete a node which has both left and right children. You could move the left or the right child into the place of the deleted node, but what do you then do about the other child and its subtree?
Solution is this; you locate the logical successor to the node being deleted. By logical successor, I mean this; say you have a tree made of integers and you delete node with value 35, the logical successor is the next largest number. Ya? if you were doing an in-order walk, it would be the element you come to after the element you're deleting.
Now, there's a simple rule to find the logical successor; you go right one (you always have a right, because this is the case where you have two children) and then you go as far left as you can.
That element you end up at is the logical successor. It's larger than the deleted element (you went right at the start, remember?) but it's the smallest next largest element.
Now, that element ALWAYS has only one or no children - because you went left as far as you can, remember? so you can't go left any more - because there is no left - so that element has no children or just a right child and that means it falls into one of the easy-to-unlink catagories (no children or just one child). So unlinking this element is easy.
Now comes the cool bit - consider this; if that next largest element were in the same place in the tree as the element you want to delete, the tree would still be valid and correct - because everything to the left of each element is smaller, everything to the right is larger.
So what you do is this; you copy the user data in the next largest node into the node being deleted and you delete that next largest node (it has no children or just a right child, so it's easy to unlink and delete).
And that's it!
So, basically - find your logical successor, unlink him from the tree and put his user data into the element you're actually originally deleting (which you don't then delete, of course, because it's still physically part of the tree).
First off, you mentioned you aren't using recursion but each function has a logical path that calls itself.
On to the questions:
1)
Remove the recursion. This can get you in a lot of trouble if your tree is large enough to blow your stack. Gcc has limited support for tail recursion, but I wouldn't count on it.
2)
Typically, when you delete a child with two nodes, you promote the left or right node to the position the deleted node was in. (This is a highly simplistic case, I'm assuming your tree isn't balanced)
2.b)
Your delete code has some problems. I'd recommend walking through it with a few hypothetical situations. Immediately obvious to me was free'ing a pointer and then deferencing it:
free(cliPtr);
cliPtr->clientProfile = NULL;
Of course, you can always worry about style once you get the correctness thing squared away.
Ideally there are three cases for deletion of a node in BST:
Case 1:
X has no children: remove X
Case 2:
X has one children : Splice out X
Case 3:
X has two children : swap X with its successor and follow case #1 or #2
So for the missing delete case:
When X (node to delete) has two children, replace X with the successor of X and follow case #1 or case #2. You can also replace with its predecessor, might be a good alternative.
if ( X->left && X->right)
{
NODE *Successor = FindSuccessor(X);
X->data = Successor->data;
free(Successor);
}
this binary codes are insert, delete,search, and quit.
Examples:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.*;
public class Binary Tree {
public static void main(String[] args) throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
LinkedList ll = new LinkedList();
ll.add("\n"+"mai 0020");
ll.add("\n"+"king 0019");
ll.add("\n"+"maan 0002");
ll.add("\n"+"dimple 0024");
ll.add("\n"+"eman 0004");
ll.add("\n"+"lara 0005");
ll.add("\n"+"cute 0008");
ll.add("\n"+"irene 0011");
ll.add("\n"+"sheena 0030");
ll.add("\n"+"aisy 0003");
System.out.println("display: " + ll);
System.out.println("\n\n");
for(int c=0; c<=10; c++) {
System.out.println("select from: 1-insert, 2-delete," +
" 3-display, 4-search, 5-quit");
String x = br.readLine();
int y = Integer.parseInt(x);
switch (y) {
case 1: //inserting
System.out.println("input name");
String n= br.readLine();
System.out.println("input a list number");
String o = br.readLine();
int z = Integer.parseInt(o);
ll.add("\n"+n+" "+z);
break;
case 2: // delete
ll.removeFirst();
break;
case 3: //Display
System.out.println("\n\n"+"List of employee: " + ll);
System.out.println("\n\n");
break;
case 4: //search
System.out.println("\n");
System.out.println("Search");
System.out.println("first element of the Linkedlist is: "
+ ll.getFirst());
System.out.println("\n\n");
System.out.println("last element of linkedlist:"
+ ll.getLast());
break;
case 5: //quit
System.out.println("\n\n\n\n\n"
+ " Thank You Very Much!!!!!!!\n\n\n");
System.exit(0);
break;
}
}
}
}
int delete_value(Tree*&root,Tree*&find,Tree*&ptr,int numb){
if(find->value==number){
//the number exist in the root,so we should find the highest value inside the right brache and replace it with the root.
Tree*ptr2=NULL;
Tree*ptr3=NULL;//pointer pointing to the parent of the last element of ptr2.
ptr2=root->right;
while(ptr2!=NULL){
ptr3=ptr2;
ptr2=ptr2->left;
}
if(ptr2->right!=NULL){
ptr3->left=ptr2->right;
}
swap(ptr2->value,root->value);
delete ptr2;
ptr2=ptr3=NULL;
}
else{
while(find->value!=numb){
if(find->value!=numb){
ptr=find;
}
if(find->value < numb){
find=find->right;
return delete_value(root,find,ptr,numb);
}
else{
find=find->left;
return delete_value(root,find,ptr,numb);
}
}//end of while
}//end of else
//the pointer find is pointing at the element we want to delete.
//the pointer ptr is pointing at the element before the one's we want to delete.
//case 1:the element to delete don't have any children
if(find->right==NULL && find->left==NULL){
if(ptr->left=find){
ptr->left=NULl;
delete find;
}
else{
ptr->right=NULL;
delete find;
}
}//end of the first case.
//case 2:the element has one child it could be to the left or to the right.
//a-child to the right.
if( find->right!=NULL && find->left==NULL ){
Tree*ptr2=find->right;
while(ptr2!=NULL){
ptr2=ptr2->left;//find the highest value in the right branche and replace it with the delete element
}
swap(find->value,ptr2->value);
delete ptr2;
ptr2=NULL;
}
//b-child to the left.
if(find->right==NULL && find->left!=NULL){
Tree*ptr2=find->left;
//check wether the find element is to the right or to the left of ptr.
if(ptr->left==find){
ptr->left=ptr2;
delete find;
}
else{
ptr->right=ptr2;
delete find;
}
}//end of the second case.
//case3: the element has to children.
if(find->right!=NULL&&find->left!=NULL){
Tree*ptr2=find->left;
while(ptr2->right!=NULL){
ptr2=ptr2->right;
}
swap(ptr2->value,find->value);
delete ptr2;
ptr2=NULL;
}//end of case 3.
}//end of the function.