二叉树的中序遍历非递归方法（算法导论第三版12.1-3）

1⃣️用栈实现

template<typename T>
void inorder_tree_walk_non_recursion_by_stack(BinaryTreeNode<T> *node)
{Stack<BinaryTreeNode<T>*> stack;stack.push(node);while (!stack.empty()){BinaryTreeNode<T> * current = stack.pop();if(current->right!= nullptr)stack.push(current->right);std::cout<<current->key<<" ";if(current->left!= nullptr)stack.push(current->left);}
}

2⃣️非栈实现

template<typename T>
void inorder_tree_walk_non_recursion(BinaryTreeNode<T>* node)
{BinaryTreeNode<T>*  perv = nullptr;BinaryTreeNode<T>* current = node;while (current!= nullptr){if(current->parent == perv){std::cout<<current->key<<" ";perv = current;if(current->left!= nullptr){current = current->left;}else if(current->right!= nullptr){current = current->right;}elsecurrent = current->parent;}else if(current->right!= nullptr && perv == current->left){perv = current;current = current->right;}else{perv = current;current = current->parent;}}
}

辅助类
1⃣️BinaryTreeNode地址
2⃣️Stack地址

测试代码

    BinaryTreeNode<int>* node1 = new BinaryTreeNode<int>(1);BinaryTreeNode<int>* node2 = new BinaryTreeNode<int>(2);BinaryTreeNode<int>* node3 = new BinaryTreeNode<int>(3);BinaryTreeNode<int>* node4 = new BinaryTreeNode<int>(4);BinaryTreeNode<int>* node5 = new BinaryTreeNode<int>(5);BinaryTreeNode<int>* node6 = new BinaryTreeNode<int>(6);BinaryTreeNode<int>* node7 = new BinaryTreeNode<int>(7);BinaryTreeNode<int>* node8 = new BinaryTreeNode<int>(8);node1->left = node2;node1->right = node3;node2->parent = node1;node2->left = node4;node2->right = node5;node3->parent = node1;node3->left = node6;node3->right = node7;node4->parent = node2;node4->left = node8;node5->parent = node2;node6->parent = node3;node7->parent = node3;node8->parent = node4;inorder_tree_walk_non_recursion_by_stack(node1);cout<<endl;inorder_tree_walk_non_recursion(node1);cout<<endl;