【二叉树的内存管理】创建和释放一棵二叉树

1. typedef struct MyTreeNode
2. {
3.  struct MyTreeNode* left; 
4.  struct MyTreeNode* right; 
5.  char data;
6. }MyTreeNode;

1. MyTreeNode * create_tree()
2. {
3.  MyTreeNode* node = NULL;
4.  char c;
5.  scanf("%c", &c);
6.  if (c == '#')
7.  {
8.    node = NULL;
9.  }
10.   else
11.   {
12.     node = (MyTreeNode*)malloc(sizeof(MyTreeNode));
13.     node->data = c;
14.     node->left = create_tree();
15.     node->right = create_tree();
16.   }
17.   return node;
18. }

1. void free_tree(MyTreeNode* tree)
2. {
3.  if (tree != NULL)
4.  {
5.    if (tree->left != NULL)
6.    {
7.      free_tree(tree->left);
8.      tree->left = NULL;
9.    }
10.     if (tree->right != NULL)
11.     {
12.       free_tree(tree->right);
13.       tree->right = NULL;
14.     }
15.     free(tree);
16.     tree = NULL;
17.   }
18. }

1. #define  _CRT_SECURE_NO_WARNINGS 
2. #include <stdlib.h>
3. #include <string.h>
4. #include <stdio.h>
5. 
6. //树结点结构体
7. typedef struct MyTreeNode
8. {
9.  struct MyTreeNode* left; 
10.   struct MyTreeNode* right; 
11.   char data;
12. }MyTreeNode;
13. 
14. //二叉树的前序遍历
15. void preorder_traversal(MyTreeNode* tree)
16. {
17.   if (tree == NULL)
18.   {
19.     return;
20.   }
21.   printf("%c ", tree->data);
22.   preorder_traversal(tree->left);
23.   preorder_traversal(tree->right);
24. }
25. 
26. //创建一颗二叉树（先创建根，后创建左子树，再创建右子树）
27. MyTreeNode * create_tree()
28. {
29.   MyTreeNode* node = NULL;
30.   char c;
31.   scanf("%c", &c);
32.   if (c == '#')
33.   {
34.     node = NULL;
35.   }
36.   else
37.   {
38.     node = (MyTreeNode*)malloc(sizeof(MyTreeNode));
39.     node->data = c;
40.     node->left = create_tree();
41.     node->right = create_tree();
42.   }
43.   return node;
44. }
45. 
46. //释放一颗二叉树（先释放左右子树，后释放根）
47. void free_tree(MyTreeNode* tree)
48. {
49.   if (tree != NULL)
50.   {
51.     if (tree->left != NULL)
52.     {
53.       free_tree(tree->left);
54.       tree->left = NULL;
55.     }
56.     if (tree->right != NULL)
57.     {
58.       free_tree(tree->right);
59.       tree->right = NULL;
60.     }
61.     free(tree);
62.     tree = NULL;
63.   }
64. }
65. 
66. int main()
67. {
68.   MyTreeNode* tree = create_tree();
69. 
70.   printf("前序遍历：");
71.   preorder_traversal(tree);
72.   printf("\n");
73. 
74.   free_tree(tree);
75. 
76.   system("pause");
77.   return 0;
78. }