后序遍历二叉树

public static void postOrderStack(Node root){
if(root==null)return;
Stack<Node> s=new Stack<Node>();
Map<Node,Boolean> map=new HashMap<Node,Boolean>();
s.push(root);
while(!s.isEmpty()){
Node temp=s.peek();
if(temp.left!=null&&!map.containsKey(temp.left)){
temp=temp.left;
while(temp!=null){
if(map.containsKey(temp))break;
else s.push(temp);
temp=temp.left;
}
continue;
}
if(temp.right!=null&&!map.containsKey(temp.right)){
s.push(temp.right);
continue;
}
Node t=s.pop();
map.put(t,true);
System.out.println(t.value);
}
}