BST remove/delete node - root - c++

Question

I got a problem when I delete root node for example if I add to tree 2, 1, 3 and remove 2 (root) something goes wrong when I want to see my tree in preorder and program fails.
Could You explain what's going wrong?
#include <iostream>
#include <string>
using namespace std;
struct BST {
int data;
BST* left;
BST* right;
};
BST* GetNewNode (int data)
{
BST* newNode = new BST ();
newNode->data = data;
newNode->left = NULL;
newNode->right = NULL;
return newNode;
}
//******************************BST******************************************************
BST * insertBST (BST * root, int data);
BST * search (BST* root , int data);
BST* FindMin(BST* root);
BST* Delete (BST* root, int data);
BST* DeleteAll(BST* root);
void Inorder(BST *root);
void Preorder(BST *root);
void Postorder(BST *root);
//****************************MAIN***********************************
int main()
{
BST* root = NULL;
string menu= " ";
int f ;
while(menu!="k")
{
cout<<"Chose function (i, r, in ,pre, post, del, f)"<<endl
<<"Want to quit tap k"<<endl;
cin>>menu;
if(menu== "i" )
{
cout<<"If you want to end inserting write 0"<<endl;
cin>>f;
while(f)
{
root = insertBST (root,f );
cin>>f;
}
}
else if(menu == "r" )
{
cout<<"Insert data of node to delete"<<endl;
cin>>f;
Delete(root , f);
}
else if(menu == "in")
Inorder (root);
else if(menu == "pre")
Preorder (root);
else if(menu == "post")
Postorder (root);
else if(menu == "del")
root = DeleteAll(root);
else if(menu == "find")
{
cin>> f;
search(root , f);
}
}
DeleteAll (root);
return 0;
}
///---------------------------------------
BST* insertBST (BST* root, int data)
{
if (root == NULL)
{
root = GetNewNode (data);
}
else if (data <= root->data)
{
root->left = insertBST (root->left, data);
}
else
{
root->right = insertBST (root->right, data);
}
return root;
}
BST* search (BST* root , int data)
{
if (root == NULL) {cout <<"Not found "<<endl; return NULL;}
else if (root->data == data){ cout<<"Found "<<root->data <<endl ;return root;}
else if (data<= root->data) return search (root->left, data);
else return search (root->right, data);
}
BST* Delete (BST* root, int data)
{
if(root == NULL) return root;
else if(data < root->data) root->left = Delete(root->left,data);
else if(data > root->data) root->right = Delete(root->right, data);
else
{
if(root->left == NULL && root->right == NULL)
{
delete root;
root = NULL;
} else if(root->left == NULL)
{
struct BST *temp = root;
root = root->right;
delete temp;
} else if(root->right == NULL)
{
struct BST *temp = root;
root = root->left;
delete temp;
} else{
struct BST *temp = FindMin(root->right);
root->data = temp->data;
root->right = Delete(root->right, temp->data);
}
}
return root;
}
void Inorder(BST *root)
{
if(root == NULL) return;
Inorder(root->left);
cout<<root->data<<" ";
Inorder(root->right);
}
void Preorder(BST *root)
{
if (root != NULL)
{
cout<< root->data<<" ";
Preorder (root->left);
Preorder (root->right);
}
else if (root == NULL)
return;
}
void Postorder(BST *root)
{
if (root == NULL)
return;
Postorder (root->left);
Postorder (root->right);
cout<< root->data<<" ";
}
BST* FindMin(BST* root)
{
while(root->left != NULL) root = root->left;
return root;
}
BST* DeleteAll(BST* root)
{
if (root!=NULL)
{
DeleteAll(root->left);
DeleteAll(root->right);
delete(root);
root = NULL;
}
return root;
}

Answer 1

What you are doing is called inorder. below you can check preorder
Preorder:
do stuff with the node // pre means before
recurse left
recurse right
void Preorder(BST *root)
{
if (root == NULL)
return;
cout<< root->data<<" ";
Preorder (root->left);
Preorder (root->right);
}