void NoRecursePreTraverse(BiTree tree){
    stack<BiNode *> stack;
    BiNode *node = tree;

    while(node != NULL || !stack.empty()){
        while(node != NULL){
        cout << node->data <<"  ";
        stack.push(node);
        node = node->lchild;
        }
        if(!stack.empty()){
            node = stack.top();
            node = node->rchild;
            stack.pop();
        }
    }

}

void NoRecurseInTraverse(BiTree tree){
    stack<BiNode *> stack;
    BiNode *node = tree;

    while(node != NULL || !stack.empty()){
        while(node != NULL){
        stack.push(node);
        node = node->lchild;
        }
        if(!stack.empty()){
            node = stack.top();
            cout << node->data << "  ";
            stack.pop();
            node = node->rchild;
        }
    }

}
struct BiTree_Flag{
    BiNode *node;
    bool flag;
};
void NoRecursePostTraverse(BiTree tree){

    stack<BiTree_Flag> stack;
    BiNode *node = tree;
    BiTree_Flag node_flag;

    while(node != NULL || !stack.empty()){
        while(node != NULL){
            node_flag.node = node;
            node_flag.flag = false;
            stack.push(node_flag);
            node = node->lchild;
        }
        if(!stack.empty()){
            node_flag = stack.top();
            stack.pop();
            if(node_flag.flag == false){
                node_flag.flag = true;
                stack.push(node_flag);
                node = node_flag.node;
                node = node->rchild;
            }else{
                cout << node_flag.node->data << "  ";
            }
        }
    }

}
 

  2）中序遍歷：根節點入棧，訪問左子樹。如果左子樹為空，棧彈出根節點，訪問根節點，訪問右子樹。

3）後續遍歷：定義新的資料結構，為每一個節點定義一個標誌位flag，false代表訪問過一次，true代表訪問過兩次。

根節點入棧，flage設為FALSE。訪問左子樹。左子樹為空，根節點彈出，如果flag為false，設為true，

訪問右節點。如果為flag為true，訪問該節點。