Can anyone help me with my binary search tree - c

Question

I'm a computer engineering student and I have to write BST as an assignment but the code is not like what everyone written(so far as I search for some example,so I'm desperate now) Here is my code so far(My classroom use C as a main language not C++)
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
typedef struct bst_node
{
int data;
struct bst_node *right;
struct bst_node *left;
}BST_NODE;
typedef struct bst
{
int size;
BST_NODE *root;
}BST;
void print(BST_NODE *pos)
{
printf("%d(0)",pos->data);
if(pos->left != NULL)
{
printf("%d(L)\n",pos->left->data);
pos=pos->left;
}
if(pos->right != NULL)
{
printf("%d(R)\n",pos->right->data);
pos=pos->right;
}
if(pos->left != NULL)
print(pos->left);
if(pos->right != NULL)
print(pos->right);
}
int main()
{
int number;
BST b;
BST_NODE *pos;
b.root=NULL;
while(1)
{
scanf("%d",&number);
printf("value=%d",number);
if(number<=0)
break;
if(b.root==NULL)
{
b.root=(BST_NODE*)malloc(sizeof(BST_NODE));
pos=b.root;
pos->data=number;
pos->left=NULL;
pos->right=NULL;
}
else
{
pos=b.root;
while(pos)
{
if(number>pos->data)
{
if(pos->right==NULL)
{
pos->right=(BST_NODE*)malloc(sizeof(BST_NODE));
pos->right->left=NULL;
pos->right->right=NULL;
pos->right->data= number;
pos=pos->right;
}
else
{
pos->right->data= number;
pos=pos->right;
}
}
if(number<pos->data)
{
if(pos->left==NULL)
{
pos->left=(BST_NODE*)malloc(sizeof(BST_NODE));
pos->left->left=NULL;
pos->left->right=NULL;
pos->left->data=number;
pos=pos->left;
}
else
{
pos->left->data=number;
pos=pos->left;
}
}
}
}
}
print(b.root);
return 0;
}
I don't know what wrong with this code because it can only receives 2 value then it stops working. The only thing I found out so far to be a problem is while(pos)loop and I try to fix this for week.I would be grateful,if anyone help me solve this problem. Print it out to would be great.
P.S -stop working mean the windows I run program in just freeze or hang.

Answer 1

You want to break out of your while(pos) loop as soon as you malloc a new node. You are done inserting so stop working.
Also you don't want to overwrite all ->data values while traversing the tree in your else branches.

Answer 2

When you add a value to the tree, it looks like you always replace the existing value with the input number instead of just traversing to the next level. Remove
pos->right->data = number;
And
pos->left->data = numbér;
From main()
You also should add an 'else' before the left node check. As it stands, you're checking the right branch and then the left branch every time through the loop. If you check the right branch and make a hit, you'll always check the left branch, too. Probably not a problem, but unnecessary.
Not sure that's the reason 'it stops working' as 'it stops working' is awful darn vague, but that looks suspicious to me.
Additionally...
Be consistent on your indentation. Sometimes the indentation is more spaces than other times
add spaces between struct definitions and Breen function declarations. Think of these things as chapters in a book. Use the whitespace to make separate things clearly separate.
add a prompt within the loop to indicate that it's expecting input. If you think your app has frozen, it may simply be waiting for input
add a check at the start of print() and sensibly handle null roots. This could occur if you type a negative number as your input the first time around. Missing such a check and typing a negative as your first input may crash.
Oh! And use calloc() instead of malloc(). Calloc initializes new memory to nulls, while malloc does not. Malloc just gives you whatever memory it happens to give you, containing whatever random garbage it may contain. If you use calloc, you will have less liklihood of issues with bad memory.