Thread: Binary tree wont go left!!!

Hello,
I am new to programming and cant figure out this problem. The program works fine if i use int numbers but breaks when i change to names of type string.
the total code is at
C++ pastebin - collaborative debugging tool
but the place i am stuck at is

Code:

void addNode(string name, int weight)
	{
		treeNode *newNode = new treeNode(name, weight);			
		if (root == 0)									
		{
			root = newNode;
			return;
		}
		treeNode *temp = root;							
		while(true)
		{
		if (temp->left != 0 && temp->name <= name)						
				if (temp->left == 0)					
				{
					temp->left = newNode;
					break;
				}
				else									// move to subtree
					temp = temp->left;
			else if (name < temp->name)					
					if (temp->right == 0)					
					{
						temp->right = newNode;
						break;
					}
					else									// move to subtree
						temp = temp->right;
				  else if(name > temp->name)
						temp = temp->right;
			//else if (name == temp->name)				
				return;
		}
	}

the code always goes to the right when I debug.
any insight would be wonderfull
thanks

Code:

if (temp->left != 0 && temp->name <= name)						
				if (temp->left == 0)					
				{
					temp->left = newNode;
					break;
				}
				else									// move to subtree
					temp = temp->left;
			else if (name < temp->name)					
					if (temp->right == 0)					
					{
						temp->right = newNode;
						break;
					}
					else									// move to subtree
						temp = temp->right;
				  else if(name > temp->name)
						temp = temp->right;
			//else if (name == temp->name)				
				return;
		}

I would add curly brackets around every if/else if/else block here to ensure it is doing what you think/want it to do. Its incredibly difficult to read and trace this manually. In addition, its good practice to always have these brackets around even 1 line if/whatever blocks of code.

I havent looked at all of the code, but heres something probably isnt what you want

Code:

if (temp->left != 0 && temp->name <= name)						
				if (temp->left == 0)

The inner if statement checks that the left is null, but its guaranteed to not be null, because the outer if checked if it was != 0. I would look around in your code for other similar logic errors like this, in addition to adding braces around every block, even for 1 line blocks. For starters, at least.

Code:

if (temp->left != 0 && temp->name <= name)

This will fail in the second entry itself.First time the root gets allocated, next time root's left is 0 , so going by your if condition it never enters the left if block, same is the case for inserting a node in the 'right' position of the root.

Here's the pseudo code.

Code:

   T*temp = root;
   while (node position not determind) {
       if (name <= temp-> name)
           if (node found at left)
               set your temp to temp->left
           else  
               postion found.Insert node and break 
      
      else if (name > temp-> name)
            if (node found at right)
                  set temp to temp->right
              else
                  postion found.Insert node and break 
             
   }