//后序遍历的非递归

public void postorderTraversa2(TreeNode root)

{

Stack<TreeNode> s = new Stack<TreeNode>();

TreeNode cur=null; //当前结点

TreeNode pre=null; //前一次访问的结点

s.push(root);

while(!s.empty())

{

cur=s.peek();

if((cur.left==null&&cur.right==null)||

(cur!=null&&(pre==cur.left||pre==cur.right)))

{

list.add(cur.val); //如果当前结点没有孩子结点或者孩子节点都已被访问过

s.pop();

pre=cur;

}

else

{

if(cur.right!=null)

s.push(cur.right);

if(cur.left!=null)

s.push(cur.left);

}

}

}

///////

--------------------------------

Node<Integer> rNode = null;

Node<Integer> current = root;

Srack <Integer> stack = new Stack<Integer>();

while(current != null || !stack.isEmpty()) {

while(current != null) {

stack.push(current);

current = current.getLeftChild();

}

current = stack.pop();

while (current != null && (current.getRightChild() == null ||current.getRightChild() == rNode)) {

System.out.print(current.getValue());

rNode = current;

if (stack.isEmpty()){

System.out.println();

return;

}

current = stack.pop();

}

stack.push(current);

current = current.getRightChild();

}