Insertion of binary search tree

If the original tree is empty, generate and return a binary search tree
with a node. If it is not empty, X is compared with the key value of the root node of the tree.
If X is large, insert to the right subtree.
If X is small, then to the left Subtree insertion

//定义二叉树 
typedef struct TreeNode *BinTree;
typedef BinTree Position;
typedef int ElementType;
struct TreeNode
{
	ElementType data;
	BinTree left;
	BinTree right;
};

BinTree Insert(ElementType x,BinTree bst)
{
	if(!bst)		//如果为空，生成并返回只有一个结点的二叉树 
	{
		bst=(BinTree)malloc(sizeof(TreeNode));
		bst->data=x;
		bst->left=bst->right=NULL;
	}
	else
	{
		if(x<bst->data)
			bst->left=Insert(x,bst->left);
		else if(x>bst->data)
			bst->right=Insert(x,bst->right);
		//x已经存在，什么都不做 	 
	}
	return bst; 
}