二元查找树转换成一个排序的双向链表

输入一棵二元查找树，将该二元查找树转换成一个排序的双向链表。要求不能创建任何新的结点，只调整指针的指向。

最直观的一种思路就是每次从二分查找树中找到最小的数，加到链表中

</pre><pre name="code" class="cpp">// BST2list.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h" 
#include<iostream> 
using namespace std;
#define INFINITY 1000000
struct BiNOde
{
	int ele;
	BiNOde* lnode;
	BiNOde* rnode;
};
int min;
BiNOde*head, *tail;
BiNOde*minnode;
BiNOde*p;
BiNOde*create_tree()
{
	BiNOde * root = new BiNOde;
	BiNOde*node1 = new BiNOde;
	BiNOde*node2 = new BiNOde;
	BiNOde*node3 = new BiNOde;
	BiNOde*node4 = new BiNOde;
	BiNOde*node5 = new BiNOde;
	BiNOde*node6 = new BiNOde;
	BiNOde*node7 = new BiNOde;
	BiNOde*node8 = new BiNOde;
	BiNOde*node9 = new BiNOde;
	BiNOde*node10 = new BiNOde;
	BiNOde*node11 = new BiNOde;
	root->ele = 45;
	node1->ele = 38;
	node2->ele = 55;
	node3->ele = 33;
	node4->ele = 43;
	node5->ele = 19;
	node6->ele = 16;
	node7->ele = 52;
	node8->ele = 58;
	node9->ele = 50;
	node10->ele = 41;
	node11->ele = 35;
	root->lnode = node1;
	root->rnode = node2;
	node1->lnode = node3;
	node1->rnode = node4;
	node2->lnode = node7;
	node2->rnode = node8;
	node3->lnode = node5;
	node3->rnode = node11;
	node4->lnode = node10;
	node4->rnode = NULL;
	node5->lnode = node6;
	node5->rnode = NULL;
	node6->lnode = NULL;
	node6->rnode = NULL;
	node7->lnode = node9;
	node7->rnode = NULL;
	node8->lnode = NULL;
	node8->rnode = NULL;
	node9->lnode = NULL;
	node9->rnode = NULL;
	node10->lnode = NULL;
	node10->rnode = NULL;
	node11->lnode = NULL;
	node11->rnode = NULL;
	//BiNOde*node12 = new BiNOde;  
	//node12->ele = 12;  
	//node12->lnode = NULL;  
	//node12->rnode = NULL;  
	//node6->lnode = node11;  
	return root;
}

BiNOde*find_min(BiNOde*node)
{
	//minnode=node;这一句会使递归出错
	if (node == NULL)
		return NULL;
	if (node->ele < min)
	{
		min = node->ele;
		minnode = node;
	}
	if (node->lnode != NULL)
	{
		if (node->lnode->ele < min)
		{
			min = node->lnode->ele;
			minnode = node->lnode;
		}
		find_min(node->lnode);
	}
	if (node->rnode != NULL)
	{
		if (node->rnode->ele < min)
		{
			min = node->rnode->ele;
			minnode = node->rnode;
		}

		find_min(node->rnode);
	}
	return minnode;
}

void findparent(BiNOde*node, BiNOde*parent)
{
	if (parent == NULL)
		return;
	if (parent->lnode == node || parent->rnode == node)
		{p = parent;return;}
	findparent(node, parent->lnode);
	findparent(node, parent->rnode);
}


BiNOde*BST2list(BiNOde*root)
{
	min = INFINITY;
	minnode = NULL;
	BiNOde*n = find_min(root);

	while (n)
	{
		if (n == root)
		{
			if (n->rnode != NULL)
				root = n->rnode;
			else
			{
				tail->rnode = n;
				n->lnode = tail;
				tail = n;
				return head;
			}

		}
		else
			if (n->rnode != NULL)
			{
			p = NULL;
			findparent(n, root);
			if (p != NULL)
				p->lnode = n->rnode;
			n->rnode = NULL;
			}
			else
			{
				p = NULL;
				findparent(n, root);
				if (p != NULL)
					p->lnode = NULL;
			}
		if (head == NULL&&tail == NULL)
		{
			head = tail = n;

		}
		else if (head == tail)
		{
			tail->rnode = n;
			n->lnode = tail;
			tail = n;
			head->rnode = tail;

		}
		else
		{
			tail->rnode = n;
			n->lnode = tail;
			tail = n;
		}
		min = INFINITY;
		minnode = NULL;
		n = find_min(root);
	}

}



int _tmain(int argc, _TCHAR* argv[])
{

	head = tail = NULL;
	BiNOde*root = create_tree();
	head = BST2list(root);


	system("pause");
	return 0;
}

find_min递归时minnode数据放的位置不对，造成开始递归失败。所以要特别注意以影响递归过程的变量的处理。

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