1 /*************************************************************************
2 > File Name: 25_BSTConvert.cpp
3 > Author: Juntaran
4 > Mail: JuntaranMail@gmail.com
5 > Created Time: 2016年08月31日 星期三 15时06分28秒
6 ************************************************************************/
7
8 #include <stdio.h>
9 #include <malloc.h>
10
11 // 二叉树结构体
12 struct TreeNode
13 {
14 int val;
15 TreeNode* left;
16 TreeNode* right;
17 };
18
19 // 构造二叉搜索树
20 TreeNode* InsertNode(TreeNode* tree, int val)
21 {
22 if (tree == NULL)
23 {
24 tree = new TreeNode();
25 tree->left = NULL;
26 tree->right = NULL;
27 tree->val = val;
28 }
29 else if (tree->val > val)
30 tree->left = InsertNode(tree->left, val);
31 else if (tree->val < val)
32 tree->right = InsertNode(tree->right, val);
33 return tree;
34 }
35
36 void PrintTree(TreeNode* tree)
37 {
38 if (tree == NULL)
39 return;
40 PrintTree(tree->left);
41 printf("%d ", tree->val);
42 PrintTree(tree->right);
43 }
44
45 void PrintList(TreeNode* list)
46 {
47 printf("\n");
48 if (list == NULL)
49 return;
50 TreeNode* node = list;
51 while (node)
52 {
53 printf("%d ", node->val);
54 node = node->right;
55 }
56 printf("\n");
57 }
58
59 /************************************************************************/
60 // 剑指Offer写法
61 void ConvertNode(TreeNode* node, TreeNode** last)
62 {
63 if (node == NULL)
64 return;
65
66 TreeNode* current = node;
67
68 // 对tree的左子树进行转换，last是转换后链表最后一个结点的指针
69 if (current->left != NULL)
70 ConvertNode(current->left, last);
71 // 调整tree的left指针，指向上一个结点
72 current->left = *last;
73 // 调整指向最后一个结点，right指向下一个结点
74 if (*last != NULL)
75 (*last)->right = current;
76
77 // 调整指向最后链表一个结点的指针
78 *last = current;
79
80 // 对tree的右子树进行转换，last是转换后链表最后一个结点的指针
81 if (current->right != NULL)
82 ConvertNode(current->right, last);
83 }
84
85 // 二叉搜索树转换为排序双向链表
86 TreeNode* Convert(TreeNode* root)
87 {
88 if (root == NULL)
89 return NULL;
90
91 TreeNode* last = NULL;
92 ConvertNode(root, &last);
93
94 TreeNode* head = root;
95 // 找到最左边的结点，即转换后链表的头结点
96 while (head && head->left)
97 head = head->left;
98 return head;
99 }
100 /************************************************************************/
101
102 /************************************************************************/
103 // 一个递归写法
104
105 TreeNode* leftLast = NULL;
106 TreeNode* Convert2(TreeNode* root)
107 {
108 if (root == NULL)
109 return root;
110 if (root->left==NULL && root->right==NULL)
111 {
112 leftLast = root;
113 return root;
114 }
115
116 // 左子树改造为双链表
117 TreeNode* left = Convert2(root->left);
118 // 左子树链表不为空，root追加到左子树链表
119 if (left != NULL)
120 {
121 leftLast->right = root;
122 root->left = leftLast; // 构造双向链表
123 }
124 leftLast = root;
125 // 右子树改造为双链表
126 TreeNode* right = Convert2(root->right);
127 // 右子树链表不为空，链表追加到root后
128 if (right != NULL)
129 {
130 right->left = root;
131 root->right = right;
132 }
133 return left != NULL ? left : root;
134 }
135 /************************************************************************/
136
137 int main()
138 {
139 TreeNode* tree = NULL;
140 for (int i = 10; i > 5; --i)
141 {
142 tree = InsertNode(tree, i);
143 }
144 for (int i = 0; i <= 5; ++i)
145 {
146 tree = InsertNode(tree, i);
147 }
148 PrintTree(tree);
149 // tree = Convert(tree);
150 tree = Convert2(tree);
151 PrintList(tree);
152
153 return 0;
154 }
