Tree not being created - c++

Question

When I call the function createBst(), the program gets terminated in the function.
I put a print statement after the function but it is not called.The next print statement "terminated" is not called
int main(){
bst b;
b.createBst();
std::cout<<"terminated"<<std::endl;
return 0;
}
class node{
public:
int val;
node* left;
node* right;
};
class bst{
public:
node* head;
void createBst();
node* newNode(int val);
};
node* bst::newNode(int v){
node n1;
node* n=&n1;
n->val=v;
n->left=nullptr;
n->right=nullptr;
return n;
}
void bst::createBst(){
head=bst::newNode(10);
head->left=bst::newNode(11);
(head->left)->left=bst::newNode(7);
head->right=bst::newNode(9);
(head->right)->left=bst::newNode(15);
(head->right)->right=bst::newNode(8);
}
the output should be "terminated".

Answer 1

For starters the classes shall be defined before their usage in main.
This function
node* bst::newNode(int v){
node n1;
node* n=&n1;
n->val=v;
n->left=nullptr;
n->right=nullptr;
return n;
}
invokes undefined behavior because it returns pointer ro a local variable n1 that will not be alive after exiting the function.
The function could be defined the following way
node* bst::newNode(int v)
{
return new node { v, nullptr, nullptr };
}
In fact the function can be a private static member function
class bst{
public:
node* head;
void createBst();
private:
static node* newNode(int val);
};
And the class node should be a nested private (or protected) class of the class bst.
Also you need either a default constructor for the class bst that will initialize head to nullptr or you have to explicitly initialize head to nullptr in the class definition like
class bst{
public:
node* head = nullptr;
void createBst();
private:
static node* newNode(int val);
};
To insert a data into the tree you should write a function for example like this
void insert( int value )
{
node **current = &head;
while ( *current != nullptr )
{
if ( value < ( *current )->val )
{
current = &( *current )->left;
}
else
{
current = &( *current )->right;
}
}
*current = newNode( value );
}