二叉树的三种迭代遍历方法

//树节点定义
struct TreeNode{
	int val;
	TreeNode * left;
	TreeNode * right;
	TreeNode(int x) : val(x), left(NULL), right(NULL){}
};

//二叉树的三种迭代遍历方法
void Preorder_iterative(TreeNode * root){
	stack<TreeNode *> sT;
	if(root)
		sT.push(root);
	while(!sT.empty()){
		TreeNode * node = sT.top();
		sT.pop();
		cout<<node->val<<endl;
		if(node->right)
			sT.push(node->right);
		if(node->left)
			sT.push(node->left);
	}
}

void Inorder_iterative(TreeNode * root){
	stack<TreeNode *> sT;
	if(root)
		sT.push(root);
	while(!sT.empty()){
		TreeNode * node = sT.top();
		sT.pop();
		while(sT->left){
			sT.push(node);
			node = node->left;
		}
		cout<<node->val<<endl;
		if(node->right)
			sT.push(node->right);
	}
}

void PostOrder_iterative(TreeNode * root){
	stack<TreeNode *> sT
	TreeNode * preVisit = NULL, curr = root;
	while(curr || !sT.empty()){
		while(curr){
			sT.push(curr);
			curr = curr->left;
		}
		curr = sT.top();
		if(curr->right == preVisit || curr->right == NULL){
			cout<<curr->val<<endl;
			preVisit = curr;
			curr = NULL;
			sT.pop();
		}
		else
			curr = curr->right;
	}
}