insertion in binary search tree (C++) - c++

Question

I'm new to data structure.
I'm making a C++ program for insertion of an element in binary search tree .
The program compiles without any error but when I'm running the program , after giving the first input n , the program stops working.
Kindly help me in making this program work properly.
My code follows up as:
#include<iostream>
#include<stdio.h>
#include<stdlib.h>
using namespace std;
struct node{
int data;
struct node* left;
struct node* right;
};
struct node *root=NULL ,*par=NULL ,*pos=NULL,*save=NULL , *ptr=NULL ;
struct node* newNode(int data)
{
struct node* newnode= (struct node*)malloc(sizeof(struct node));
newnode->data=data;
newnode->right=NULL;
newnode->left=NULL;
return newnode;
}
void findpos(int data)
{
if(root==NULL)
{
par=NULL,pos=NULL;
return;
}
if(root->data==data)
{
par=NULL , pos=root;
return;
}
if(data<root->data)
{
save=root; ptr=root->left;
}
else{
save=root; ptr=root->right;
}
while(ptr!=NULL)
{
if(ptr->data==data)
{
par=save; pos=ptr;
return;
}
if(data<ptr->data)
{
save=ptr;
ptr=ptr->left;
}
else{
save=ptr;
ptr=ptr->right;
}
}
pos=NULL; par=save;
return;
}
void insert(int data)
{
findpos(data);
if(pos!=NULL)
{
return;
}
pos=newNode(data);
if(data<par->data)
par->left=pos;
else
par->right=pos;
return;
}
int main()
{
struct node *root= newNode(4);
root->left=newNode(3);
root->left->left=newNode(2);
root->right=newNode(6);
int n;
cin>>n;
insert(n);
cout<<pos->data; //just trying to see if it works
return 0;
}

Answer 1

The root pointer declared in the main() override the global root pointer. Then at the first findpos(), the root (global) is still NULL.
So, simply replace that code:
int main()
{
struct node *root= newNode(4);
root->left=newNode(3);
root->left->left=newNode(2);
root->right=newNode(6);
int n;
cin>>n;
insert(n);
cout<<pos->data; //just trying to see if it works
return 0;
}
By this one:
int main()
{
root= newNode(4);
root->left=newNode(3);
root->left->left=newNode(2);
root->right=newNode(6);
int n;
cin>>n;
insert(n);
cout<<pos->data; //just trying to see if it works
return 0;
}

Answer 2

Changed the main method so that it modifies root in global namespace; before you were declaring a new node called root localy within main.
int main() {
// struct node *root = newNode(4); // you made this root a member of main.
// not a global member anymore.
root = newNode(4); // use this
// Populate some nodes
root->left=newNode(3);
root->left->left=newNode(2);
root->right=newNode(6);
/* tree so far:
* 4
* / \
* 3 6
* /
* 2
*/
int n;
cin >> n;
cout << "user input " << n << "\n";
insert(n);
cout << pos->data; //just trying to see if it works
return 0;
}