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1.1 root 1: /* wf1 - print word frequencies; uses structures */
2:
3: struct node {
4: int count; /* frequency count */
5: struct node *left; /* left subtree */
6: struct node *right; /* right subtree */
7: char *word; /* word itself */
8: } words[2000];
9: int next; /* index of next free entry in words */
10:
11: struct node *lookup();
12:
13: main()
14: {
15: struct node *root;
16: char word[20];
17:
18: root = 0;
19: next = 0;
20: while (getword(word))
21: lookup(word, &root)->count++;
22: tprint(root);
23: return 0;
24: }
25:
26: /* err - print error message s and die */
27: err(s)
28: char *s;
29: {
30: printf("? %s\n", s);
31: exit(1);
32: }
33:
34: /* getword - get next input word into buf, return 0 on EOF */
35: int getword(buf)
36: char *buf;
37: {
38: char *s;
39: int c;
40:
41: while ((c = getchar()) != -1 && isletter(c) == 0)
42: ;
43: for (s = buf; c = isletter(c); c = getchar())
44: *s++ = c;
45: *s = 0;
46: if (s > buf)
47: return (1);
48: return (0);
49: }
50:
51: /* isletter - return folded version of c if it is a letter, 0 otherwise */
52: int isletter(c)
53: int c;
54: {
55: if (c >= 'A' && c <= 'Z')
56: c += 'a' - 'A';
57: if (c >= 'a' && c <= 'z')
58: return (c);
59: return (0);
60: }
61:
62: /* lookup - lookup word in tree; install if necessary */
63: struct node *lookup(word, p)
64: char *word;
65: struct node **p;
66: {
67: int cond;
68: char *malloc();
69:
70: if (*p) {
71: cond = strcmp(word, (*p)->word);
72: if (cond < 0)
73: return lookup(word, &(*p)->left);
74: else if (cond > 0)
75: return lookup(word, &(*p)->right);
76: else
77: return *p;
78: }
79: if (next >= 2000)
80: err("out of node storage");
81: words[next].count = 0;
82: words[next].left = words[next].right = 0;
83: words[next].word = malloc(strlen(word) + 1);
84: if (words[next].word == 0)
85: err("out of word storage");
86: strcpy(words[next].word, word);
87: return *p = &words[next++];
88: }
89:
90: /* tprint - print tree */
91: tprint(tree)
92: struct node *tree;
93: {
94: if (tree) {
95: tprint(tree->left);
96: printf("%d\t%s\n", tree->count, tree->word);
97: tprint(tree->right);
98: }
99: }
100:
101: /* strcmp - compare s1 and s2, return <0, 0, or >0 */
102: int strcmp(s1, s2)
103: char *s1, *s2;
104: {
105: while (*s1 == *s2) {
106: if (*s1++ == 0)
107: return 0;
108: ++s2;
109: }
110: if (*s1 == 0)
111: return -1;
112: else if (*s2 == 0)
113: return 1;
114: return *s1 - *s2;
115: }
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