1 #include <stdio.h>
2 #include <stdlib.h>
3
4 struct tree
5 {
6 char info;
7 struct tree *left;
8 struct tree *right;
9 };
10
11 struct tree *root; /*树的第一个结点*/
12 struct tree *construct(struct tree *root, struct tree *r, char info);
13 void print(struct tree *r, int l);
14
15 int main(void)
16 {
17 char s[80];
18 root = NULL;
19 do
20 {
21 printf("请输入一个字符:");
22 gets(s);
23 root = construct(root, root, *s);
24 } while (*s);
25 print(root, 0);
26 getchar();
27 return 0;
28 }
29
30 struct tree *construct(
31 struct tree *root,
32 struct tree *r,
33 char info)
34 {
35 if (!r)
36 {
37 r = (struct tree *)malloc(sizeof(struct tree));
38 if (!r)
39 {
40 printf("内存分配失败！");
41 exit(0);
42 }
43 r->left = NULL;
44 r->right = NULL;
45 r->info = info;
46 if (!root)
47 return r;
48 if (info < root->info)
49 root->left = r;
50 else
51 root->right = r;
52 return r;
53 }
54 if (info < r->info)
55 construct(r, r->left, info);
56 else
57 construct(r, r->right, info);
58
59 return root;
60 }
61
62 void print(struct tree *r, int l)
63 {
64 int i;
65 if (!r)
66 return;
67 print(r->left, l + 1);
68 for (i = 0; i < l; ++i)
69 printf(" ");
70 printf("%c\n", r->info);
71 print(r->right, l + 1);
72 }
