Where is the flaw in my binary tree insertion logic? - c++

Question

My solution is like
/*
Node is defined as
typedef struct node
{
int data;
node * left;
node * right;
}node;
*/
node * insert (node * root, int value)
{
bool inTreeAlready = false;
node * cur = root;
while(cur != NULL)
{
if(cur->data < value)
cur = cur->right;
else if(cur->data > value)
cur = cur->left;
else
{
inTreeAlready = true;
break;
}
}
if(!inTreeAlready)
{
cur = new node;
cur->data = value;
cur->left = NULL;
cur->right = NULL;
}
return root;
}
where the prompt to the problem says you're supposed to return the root of the tree after insertion.
This is evidently wrong as the output is
Wrong Answer!
Some possible errors:
1. You returned a NULL value from the function.
2. There is a problem with your logic
3. You are printing some value from the function
which isn't very descriptive.
I've double-checked my logic and don't know what the deal is.

Answer 1

You didn't add the new node into the tree. Here's a modified version.
node * insert (node * root, int value)
{
bool inTreeAlready = false;
node * cur = root;
node *parent;
bool right;
while(cur != NULL)
{
parent = cur;
if(cur->data < value)
{
cur = cur->right;
right = true;
}
else if(cur->data > value)
{
cur = cur->left;
right = false;
}
else
{
inTreeAlready = true;
break;
}
}
if(!inTreeAlready)
{
cur = new node;
cur->data = value;
cur->left = NULL;
cur->right = NULL;
if(root == NULL) root = cur;
else if(right) parent->right = cur;
else parent->left = cur;
}
return root;
}