编程算法 - 二叉搜索树 与 双向链表 代码(C++)

二叉搜索树 与 双向链表 代码(C++)

本文地址: http://blog.csdn.net/caroline_wendy

题目：输入一颗二叉搜索树, 将该二叉搜索树转换成一个排序的双向链表.

要求不能创建不论什么新的结点, 仅仅能调整数中结点的指针的指向.

方法: 使用中序遍历每个结点, 并进行连接, 即左子树指前, 右子树指后, 并保存前一个节点.

本程序包括算法原理, 測试程序, 及 输出.

/*
 * main.cpp
 *
 *  Created on: 2014.6.12
 *      Author: Spike
 */

/*eclipse cdt, gcc 4.8.1*/

#include <iostream>
#include <stack>
#include <queue>

using namespace std;

struct BinaryTreeNode {
	int value;
	BinaryTreeNode* left;
	BinaryTreeNode* right;
};

void printTree (BinaryTreeNode* tree)
{
	BinaryTreeNode* node = tree;
	std::queue<BinaryTreeNode*> temp1;
	std::queue<BinaryTreeNode*> temp2;

	temp1.push(node);

	while (!temp1.empty())
	{
		node = temp1.front();
		if (node->left != NULL) {
			temp2.push(node->left);
		}

		if (node->right != NULL) {
			temp2.push(node->right);
		}

		temp1.pop();

		std::cout << node->value  << " ";

		if (temp1.empty())
		{
			std::cout << std::endl;
			temp1 = temp2;
			std::queue<BinaryTreeNode*> empty;
			std::swap(temp2, empty);
		}
	}
}

BinaryTreeNode* buildTree (const std::vector<int>& L)
{
	if (L.empty())
		return nullptr;

	std::queue<BinaryTreeNode*> parentQueue;
	std::queue<BinaryTreeNode*> childQueue;

	BinaryTreeNode* root = new BinaryTreeNode();
	root->value = L[0];

	parentQueue.push(root);

	std::size_t times = 1;
	while (times < L.size())
	{
		BinaryTreeNode* parent = parentQueue.front();
		parentQueue.pop();

		BinaryTreeNode* lchild = new BinaryTreeNode();
		lchild->value = L[times];
		lchild->left = nullptr;
		lchild->right = nullptr;
		++times;

		parent->left = lchild;
		childQueue.push(lchild);

		if (times == L.size()) break;

		BinaryTreeNode* rchild = new BinaryTreeNode();
		rchild->value = L[times];
		rchild->left = nullptr;
		rchild->right = nullptr;
		++times;

		parent->right = rchild;
		childQueue.push(rchild);

		if (parentQueue.empty()) {
			parentQueue = childQueue;
			std::queue<BinaryTreeNode*> empty;
			std::swap(childQueue, empty);
		}
	}

	return root;
}

void printList (BinaryTreeNode* pHeadOfList)
{
	while (pHeadOfList != NULL && pHeadOfList->right != NULL)
	{
		std::cout << pHeadOfList->value << " ";
		pHeadOfList = pHeadOfList->right;
	}

	std::cout << pHeadOfList->value << " ";
	std::cout << std::endl;

	return;
}

void ConvertNode(BinaryTreeNode* root, BinaryTreeNode*& pLast)
{
	if (root == NULL)
		return;

	BinaryTreeNode* current = root;

	if (current->left != NULL)
		ConvertNode(current->left, pLast);

	current->left = pLast;
	if (pLast != NULL)
		pLast->right = current;

	pLast = current;

	if (current->right != NULL)
		ConvertNode(current->right, pLast);
}

BinaryTreeNode* Convert(BinaryTreeNode* root)
{
	BinaryTreeNode* pLast = NULL;
	ConvertNode(root, pLast);

	BinaryTreeNode* head = pLast;

	while (head != NULL && head->left != NULL)
		head = head->left;

	return head;
}

int main (void)
{
	std::vector<int> L = {10, 6, 14, 4, 8, 12, 16};
	BinaryTreeNode* tree = buildTree(L);
	std::cout << "----Tree:----\n";
	printTree(tree);
	BinaryTreeNode* list = Convert(tree);
	std::cout << "----List:----\n";
	printList(list);
	return 0;
}

输出:

----Tree:----
10
6 14
4 8 12 16
----List:----
4 6 8 10 12 14 16