数据结构 - 互换二叉树中所有结点的左右子树（C++）

#include <iostream>

#define NULL 0

using namespace std;

template<class T>
struct BTNode
{
	T data;
	BTNode<T> *lChild, *rChild;
	BTNode();
	BTNode(const T &val, BTNode<T> *Childl = NULL, BTNode<T> *Childr = NULL)
	{
		data = val;
		lChild = Childl;
		rChild = Childr;
	}
	BTNode<T>* CopyTree()
	{
		BTNode<T> *l, *r, *n;
		if(&data == NULL)
		{
			return NULL;
		}
		l = lChild->CopyTree();
		r = rChild->CopyTree();
		n = new BTNode<T>(data, l, r);
		return n;
	}
};

template<class T>
BTNode<T>::BTNode()
{
	lChild = rChild = NULL;
}

template<class T>
class BinaryTree
{
public:
	BTNode<T> *root;
	BinaryTree();
	~BinaryTree();
	void Pre_Order();
	void In_Order();
	void Post_Order();
	void DestroyTree();
	BTNode<T>* MakeTree(const T &element, BTNode<T> *l, BTNode<T> *r)
	{
		root = new BTNode<T> (element, l, r);
		if(root == NULL)
		{
			cout << "Failure for applying storage address, system will close the process." << endl;
			exit(1);
		}
		return root;
	}

private:
	void PreOrder(BTNode<T> *r);
	void InOrder(BTNode<T> *r);
	void PostOrder(BTNode<T> *r);
	void Destroy(BTNode<T> *&r);
};

template<class T>
BinaryTree<T>::BinaryTree()
{
	root = NULL;
}

template<class T>
BinaryTree<T>::~BinaryTree()
{
	DestroyTree();
}

template<class T>
void BinaryTree<T>::Pre_Order()
{
	PreOrder(root);
}

template<class T>
void BinaryTree<T>::In_Order()
{
	InOrder(root);
}

template<class T>
void BinaryTree<T>::Post_Order()
{
	PostOrder(root);
}

template<class T>
void BinaryTree<T>::DestroyTree()
{
	Destroy(root);
}

template<class T>
void BinaryTree<T>::PreOrder(BTNode<T> *r)
{
	if(r != NULL)
	{
		cout << r->data << ' ';
		PreOrder(r->lChild);
		PreOrder(r->rChild);
	}
}

template<class T>
void BinaryTree<T>::InOrder(BTNode<T> *r)
{
	if(r != NULL)
	{
		InOrder(r->lChild);
		cout << r->data << ' ';
		InOrder(r->rChild);
	}
}

template<class T>
void BinaryTree<T>::PostOrder(BTNode<T> *r)
{
	if(r != NULL)
	{
		PostOrder(r->lChild);
		PostOrder(r->rChild);
		cout << r->data << ' ';
	}
}

template<class T>
void BinaryTree<T>::Destroy(BTNode<T> *&r)
{
	if(r != NULL)
	{
		Destroy(r->lChild);
		Destroy(r->rChild);
		delete r;
		r = NULL;
	}
}

template<class T>
void Swap(BTNode<T> *r) // Swap left, right subtree of all nodes.
{
	BTNode<T> *p;
	if(r)
	{
		p = r->lChild;
		r->lChild = r->rChild;
		r->rChild = p; // Swap left, right child.
		Swap(r->lChild); // Swap left, right subtree of all the nodes in left subtree.
		Swap(r->rChild); // Swap left, right subtree of all the nodes in right subtree.
	}
}

void main()
{
	BTNode<char> *b, *c, *d, *e, *f, *g;
	BinaryTree<char> a;
	b = a.MakeTree('F', NULL, NULL);
	c = a.MakeTree('E', NULL, NULL);
	d = a.MakeTree('D', NULL, NULL);
	e = a.MakeTree('C', b, NULL);
	f = a.MakeTree('B', d, c);
	g = a.MakeTree('A', f, e);

	cout << "Pre Order: ";
	a.Pre_Order();
	cout << endl;

	cout << "In Order: ";
	a.In_Order();
	cout << endl;

	cout << "Post Order: ";
	a.Post_Order();
	cout << endl;

	cout << endl << "------Swap left, right subtree of all nodes------" << endl << endl;
	Swap(a.root);

	cout << "Pre Order: ";
	a.Pre_Order();
	cout << endl;

	cout << "In Order: ";
	a.In_Order();
	cout << endl;

	cout << "Post Order: ";
	a.Post_Order();
	cout << endl << endl;
}

// Output:
/*
Pre Order: A B D E C F
In Order: D B E A F C
Post Order: D E B F C A

------Swap left, right subtree of all nodes------

Pre Order: A C F B E D
In Order: C F A E B D
Post Order: F C E D B A

*/

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