public static void postOrderTraveralWithStack(TreeNode node){
Stack<TreeNode> stack = new Stack<TreeNode>();
TreeNode treeNode = node;
TreeNode lastVisit = null;   //标记每次遍历最后一次访问的节点
while(treeNode!=null || !stack.isEmpty()){//节点不为空，结点入栈，并且指向下一个左孩子
while(treeNode!=null){
stack.push(treeNode);
treeNode = treeNode.leftChild;
}
//栈不为空
if(!stack.isEmpty()){
//出栈
treeNode = stack.pop();
/**
* 这块就是判断treeNode是否有右孩子，
* 如果没有输出treeNode.data，让lastVisit指向treeNode，并让treeNode为空
* 如果有右孩子，将当前节点继续入栈，treeNode指向它的右孩子,继续重复循环
*/
if(treeNode.rightChild == null || treeNode.rightChild == lastVisit) {
System.out.print(treeNode.data + " ");
lastVisit = treeNode;
treeNode  = null;
}else{
stack.push(treeNode);
treeNode = treeNode.rightChild;
}

}

}
}