非递归周游二叉树

最新推荐文章于 2022-03-30 19:45:26 发布

superameng

最新推荐文章于 2022-03-30 19:45:26 发布

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本文介绍了二叉树的四种遍历方法：前序、中序、后序及层次遍历，并提供了不使用递归的具体实现代码。每种遍历方式都通过栈或队列辅助完成，有助于理解非递归实现的细节。

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前序周游二叉树

template <class T>
void BinaryTree<T>::PreOrderWithoutRecursion(BinaryTreeNode<T>* root)
{
	using std::stack;
	stack<BinaryTreeNode<T>*> aStack;
	BinaryTreeNode<T>* pointer = root;
	while (!aStack.empty()||pointer) {
		if (pointer) {
			Visit(pointer->value());
			aStack.push(pointer);
			pointer = pointer->leftchiled();
		} else {
			pointer = aStack.top();
			aStack.pop();
			pointer = pointer->rightchild();
		}
	}
}

中序周游二叉树

template <class T>
void BinaryTree<T>::InOrderWithoutRecursion(BinaryTreeNode<T>* root)
{
	using std::stack;
	stack<BinaryTreeNode<T>*> aStack;
	BinaryTreeNode<T>* pointer = root;
	while (!aStack.empty()||pointer) {
		if (pointer) {	
			aStack.push(pointer);
			pointer = pointer->leftchiled();
		} else {
			pointer = aStack.top();
			Visit(pointer->value());		
			pointer = pointer->rightchild();
			aStack.pop();
		}
	}
}

后序周游二叉树

template <class T>
void BinaryTree<T>::PostOrderWithoutRecursion(BinaryTreeNode<T>* root)
{
	using std::stack;
	stack<BinaryTreeNode<T>*> aStack;
	BinaryTreeNode<T>* pointer = root;
	BinaryTreeNode<T>* lastVisite = NULL;
	
	while (!aStack.empty()||pointer) {
		if (pointer) {
			aStack.push(pointer);
			pointer = pointer->leftchiled();
		} else {
			pointer = aStack.top();
			if (pointer->rightchild() == NULL || lastVisite == pointer->rightchild()) {
				Visit(pointer->value());	
				lastVisite = pointer;
				aStack.pop();
				pointer = NULL;
			} else
				pointer = pointer->rightchild();
		}
	}
}

层次周游二叉树

template <class T>
void BinaryTree<T>::PostOrderWithoutRecursion(BinaryTreeNode<T>* root)
{
	using std::queue;
	queue<BinaryTreeNode<T>*> aQueue;
	BinaryTreeNode<T>* pointer = root;
	if (pointer)
		aQueue.push(pointer);
	while(!aQueue.empty()) {
		pointer = aQueue.front();
		Visit(pointer->value());	
		aQueue.pop();
		if (pointer->->leftchiled())
			aQueue.push(pointer->->leftchiled());
		if (pointer = pointer->rightchild())
			aQueue.push(pointer = pointer->rightchild());
	}
}