我正在进行一项作业，要求我在给定的文本文件中打印前10个最常出现的单词。我的代码是打印文件中的单词，但不是根据它们的频率对它们进行排序。
以下是我的代码。我使用哈希表来存储每个唯一的单词及其频率。我目前正在使用我编写的wordcmp函数对单词进行排序，并在main中的内置qsort函数中调用它。
如果有人可以指导我修正错误，我会非常感激。
我目前的输出：
前10个单词（满分10个）是：
1 im
1是
再次1
3开心
2你好
1怎么样
1让
1你
1试试
1这个
预期输出（我想要的）：
前10个单词（满分10分）是：
3开心
2你好
1你
1试试
1这个
1让
1 im
1怎么样
1是
再次1
以下是我的一些代码：
typedef struct word
{
char *s; /* the word */
int count; /* number of times word occurs */
struct word* next;
}word;
struct hashtable
{
word **table;
int tablesize;
int currentsize;
};
typedef struct hashtable hashtable;
int main(int argc, char *argv[])
{
int top_words = 10;
word *word = NULL;
hashtable *hash = ht_create(5000);
char *file_name;
char *file_word;
FILE *fp;
struct word *present = NULL;
fp = fopen (file_name, "r");
if (fp == NULL)
{
fprintf (stderr,"%s: No such file or directory\n", file_name);
fprintf(stderr,"The top %d words (out of 0) are:\n", top_words);
exit(-1);
}
continue_program:
while ((file_word = getWord(fp)))
{
word = add(hash, file_word, 1);
}
fclose(fp);
qsort((void*)hash->table, hash->currentsize, sizeof(word),(int (*)(const void *, const void *)) wordcmp);
if(top_words > total_unique_words)
top_words = total_unique_words;
printf("the top %d words (out of %d) are:\n", top_words, total_unique_words);
int iterations =0;
for(i =0; i <= hash->tablesize && iterations< top_words; i++)
{
present = hash->table[i];
if(present != NULL)
{
printf(" %4d %s\n", present->count, present->s);
present = present->next;
iterations++;
}
}
freetable(hash);
return 0;
}
int wordcmp (word *a, word *b)
{
if (a != NULL && b!= NULL) {
if (a->count < b->count)
{
return +1;
}
else if (a->count > b->count)
{
return -1;
}
else if (a->count == b->count)
{
/*return strcmp(b->s, a->s);*/
return 0;
}
}
return 0;
}
/* Create a new hashtable. */
struct hashtable *ht_create( int size )
{
int i;
if( size < 1 )
return NULL;
hashtable *table = (hashtable *) malloc(sizeof(hashtable));
table->table = (word **) malloc(sizeof(word *) * size);
if(table != NULL)
{
table->currentsize = 0;
table->tablesize = size;
}
for( i = 0; i < size; i++ )
{
table->table[i] = NULL;
}
return table;
}
/* Adds a new node to the hash table*/
word * add(hashtable *h, char *key, int freq)
{
int index = hashcode(key) % h->tablesize;
word *current = h->table[index];
/* Search for duplicate value */
while(current != NULL) {
if(contains(h, key) == 1){
current->count++;
return current;
}
current = current->next;
}
/* Create new node if no duplicate is found */
word *newnode = (struct word*)malloc(sizeof(struct word));
if(newnode!=NULL){
newnode->s =strdup(key);
newnode-> count = freq;
newnode-> next = NULL;
}
h->table[index] = newnode;
h->currentsize = h->currentsize + 1;
total_unique_words++;
return newnode;
}
答案 0 :(得分：0)
您面临的主要问题是尝试使用存储桶的链接列表链接对哈希表进行排序。当发生哈希冲突时，您的表不会调整大小，您只需使用链接列表来存储导致冲突的单词，该单词链接到已存储在那里的单词的table[index]。这就是add的作用。
这很容易导致哈希表的内容如下所示：
table[ 0] = NULL
table[ 1] = foo
table[ 2] = NULL
table[ 3] = |some|->|words|->|that|->|collided| /* chained bucket */
table[ 4] = other
table[ 5] = words
table[ 6] = NULL
table[ 7] = NULL
...
你不能简单地qsort表，并希望获得正确的单词频率。 qsort无法知道"some"只是链接列表中的起始单词，所有qsort获取都是指向"some"和sizeof(word)的指针。
为了让生活更轻松，只需忘记哈希表，并使用动态分配的word**数组。您可以使用类似的添加来增加重复项的出现次数，并避免链接桶的所有问题。 （如果你为每个单词提供自动存储，它会给你一个简单的free()指针，你已经完成了）
以下示例需要2个参数。第一个用于读取单词的文件名，以及（可选）第二个整数值，将排序后的输出限制为最高单词数。 words_t结构使用限制为32个字符的word自动存储（未删节字典中最大的单词为28个字符）。您可以更改单词或读取以解析输入的方式，并根据需要忽略标点符号和复数。以下分隔所有标点符号（连字符除外）的单词，并丢弃复数形式的单词（例如，在遇到"Mike"时存储"Mike's"，丢弃"'s"）
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>
#define MAXC 32 /* max word length is 28-char, 29-char is sufficient */
#define MAXW 128 /* initial maximum number of words to allocate */
typedef struct {
char word[MAXC]; /* struct holding individual words */
size_t ninst; /* and the number of times they occur */
} words_t;
/* function prototypes */
void *addword (words_t *words, const char *word, size_t *wc, size_t *maxw);
void *xrealloc (void *ptr, size_t psz, size_t *nelem);
/* qsort compare function for words_t (alphabetical) */
int cmpwrds (const void *a, const void *b)
{
return strcmp (((words_t *)a)->word, ((words_t *)b)->word);
}
/* qsort compare function for words_t (by occurrence - descending)
* and alphabetical (ascending) if occurrences are equal)
*/
int cmpinst (const void *a, const void *b)
{
int ndiff = (((words_t *)a)->ninst < ((words_t *)b)->ninst) -
(((words_t *)a)->ninst > ((words_t *)b)->ninst);
if (ndiff)
return ndiff;
return strcmp (((words_t *)a)->word, ((words_t *)b)->word);
}
int main (int argc, char **argv) {
int c = 0, nc = 0, prev = ' ', total = 0;
size_t maxw = MAXW, wc = 0, top = 0;
char buf[MAXC] = "";
words_t *words = NULL;
FILE *fp = fopen (argv[1], "r");
if (!fp) { /* validate file open for reading */
fprintf (stderr, "error: file open failed '%s'.\n", argv[1]);
return 1;
}
if (argc > 2) { /* if 2 args, convert argv[2] to number of top words */
char *p = argv[2];
size_t tmp = strtoul (argv[2], &p, 0);
if (p != argv[2] && !errno)
top = tmp;
}
/* allocate/validate initial words */
if (!(words = calloc (maxw, sizeof *words))) {
perror ("calloc-words");
return 1;
}
while ((c = fgetc(fp)) != EOF) { /* read each character in file */
if (c != '-' && (isspace (c) || ispunct (c))) { /* word-end found */
if (!isspace (prev) && !ispunct (prev) && /* multiple ws/punct */
!(prev == 's' && nc == 1)) { /* exclude "'s" */
buf[nc] = 0; /* nul-terminate */
words = addword (words, buf, &wc, &maxw); /* add word */
nc = 0; /* reset char count */
}
}
else if (nc < MAXC - 1) { /* add char to buf */
buf[nc++] = c;
}
else { /* chars exceed MAXC - 1; storage capability of struct */
fprintf (stderr, "error: characters exceed %d.\n", MAXC);
return 1;
}
prev = c; /* save previous char */
}
if (!isspace (prev) && !ispunct (prev)) /* handle non-POSIX end */
words = addword (words, buf, &wc, &maxw);
if (fp != stdin) fclose (fp); /* close file if not stdin */
qsort (words, wc, sizeof *words, cmpinst); /* sort words by frequency */
printf ("'%s' contained '%zu' words.\n\n", /* output total No. words */
fp == stdin ? "stdin" : argv[1], wc);
/* output top words (or all words in descending order if top not given) */
for (size_t i = 0; i < (top != 0 ? top : wc); i++) {
printf (" %-28s %5zu\n", words[i].word, words[i].ninst);
total += words[i].ninst;
}
printf ("%33s------\n%34s%5d\n", " ", "Total: ", total);
free (words);
return 0;
}
/** add word to words, updating pointer to word-count 'wc' and
* the maximum words allocated 'maxw' as needed. returns pointer
* to words (which must be assigned back in the caller).
*/
void *addword (words_t *words, const char *word, size_t *wc, size_t *maxw)
{
size_t i;
for (i = 0; i < *wc; i++)
if (strcmp (words[i].word, word) == 0) {
words[i].ninst++;
return words;
}
if (*wc == *maxw)
words = xrealloc (words, sizeof *words, maxw);
strcpy (words[*wc].word, word);
words[(*wc)++].ninst++;
return words;
}
/** realloc 'ptr' of 'nelem' of 'psz' to 'nelem * 2' of 'psz'.
* returns pointer to reallocated block of memory with new
* memory initialized to 0/NULL. return must be assigned to
* original pointer in caller.
*/
void *xrealloc (void *ptr, size_t psz, size_t *nelem)
{ void *memptr = realloc ((char *)ptr, *nelem * 2 * psz);
if (!memptr) {
perror ("realloc(): virtual memory exhausted.");
exit (EXIT_FAILURE);
} /* zero new memory (optional) */
memset ((char *)memptr + *nelem * psz, 0, *nelem * psz);
*nelem *= 2;
return memptr;
}
（注意：输出按发生的降序排序，如果单词的出现次数相同，则按字母顺序排序）
示例使用/输出
$ ./bin/getchar_wordcnt_top dat/damages.txt 10
'dat/damages.txt' contained '109' words.
the 12
a 10
in 7
of 7
and 5
anguish 4
injury 4
jury 4
mental 4
that 4
------
Total: 61
注意：使用哈希表作为存储的基础，您必须至少创建一个指向哈希表中每个单词的指针数组，然后对指针数组进行排序。否则，您需要复制存储并将单词复制到新数组进行排序。 （这在某种程度上是一种记忆效率低下的方法）。创建一个单独的指针数组，指向哈希表中每个单词的排序，这是你必须调用qsort并避免链式存储桶问题的唯一方法。