Thread: Growing a Binary Tree

so i want to scan a string of an expression (ex: "1+2*3"), then put each of the element into a binary tree. So the operator will be the node, and the numbers will be the leaf. And below is my code:

Code:

double GrowTree(const string& expression)
{
	char number[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9'};
	char operation[] = {'+', '-', '*', '/'};
	string tempEx = expression;
	TreeNode<char>* treeRoot = new TreeNode<char>;
	TreeNode<char>* treeCurrent = new TreeNode<char>;
	treeRoot = NULL;
	treeCurrent = treeRoot;

	while(!tempEx.empty())
	{
		for(int i=0; i<sizeof(number)/sizeof(char); i++)
		{
			if(tempEx[0] == number[i])
			{
				TreeNode<char>* newLeaf = new TreeNode<char>;
				newLeaf->Value = tempEx[0];

				if ( treeCurrent == NULL )
				{
					treeRoot = treeCurrent = newLeaf;
				}else
				{
					treeCurrent->Right = newLeaf;
				}
			}
		}


			//if find any operator sign
			if( (tempEx[0] == '+' || tempEx[0]=='-'))
			{
				if(treeCurrent->Right == NULL)
				{
					TreeNode<char>* newRoot = new TreeNode<char>;
					newRoot->Value = tempEx[0];
				
					//the operator will become the root
					newRoot->Left = treeRoot;
					treeCurrent = newRoot;

					//treeRoot->Right = treeCurrent;
				}else
				{
					TreeNode<char>* newRoot = new TreeNode<char>;
					newRoot->Value = tempEx[0];
					newRoot->Left = treeCurrent->Right;
					treeCurrent->Right = newRoot;
					treeCurrent = newRoot;
					//treeRoot->Right = treeCurrent;
				}
			}else
			{
				if ( (tempEx[0] == '*' || tempEx[0] == '/' ))
				{
					if(treeCurrent->Right == NULL)
					{
						TreeNode<char>* newChild = new TreeNode<char>;
						newChild->Value = tempEx[0];					
						//the operator will become the root
						newChild->Left = treeRoot;
						treeCurrent = newChild;
						//treeRoot->Right = treeCurrent;
					}else
					{
						TreeNode<char>* newChild = new TreeNode<char>;
						newChild->Value = tempEx[0];
						newChild->Left = treeCurrent->Right;
						treeCurrent->Right = newChild;
						treeCurrent = newChild;
						//treeRoot->Right = treeCurrent;
					}
				}
			}
		
		tempEx.erase(tempEx.begin());
	
	}


	return ValueOf(treeRoot);        //This is where the function calculate the expression, which is another function
}

At the end, i had no idea how to reverse and attach everything back to the 'treeRoot'. Can someone help me? Thank you very much

I could have reduce the code a little bit at checking the operators, but you know . I'll reduce it later when i the whole thing works