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;
}
}