我已经在这个小项目上工作了很长一段时间，但我无法弄清楚为什么我没有得到预期的结果。我是 C 编程的初学者，所以我对指针和内存分配/释放的理解是新手。无论如何，我通过最初构建一个哈希函数，然后向它添加一个计数来构建这段代码。但是，当我测试它时，有时计数有效，有时无效。我不确定这是哈希函数的错，还是我设置计数的方式的错。文本文件一次读取一行，是一个由十六进制组成的字符串。
struct node {
char *data;
struct node *next;
int count; /* Implement count here for word frequencies */
};
#define H_SIZE 1024
struct node *hashtable[H_SIZE]; /* Declaration of hash table */
void h_lookup(void)
{
int i = 0;
struct node *tmp;
for(i = 0; i < H_SIZE; i++) {
for(tmp = hashtable[i]; tmp != NULL; tmp = tmp->next) {
if(tmp->data != 0) {
printf("Index: %d\nData: %s\nCount: %d\n\n", i,
tmp->data, tmp->count);
}
}
}
}
/* self explanatory */
void h_add(char *data)
{
unsigned int i = h_assign(data);
struct node *tmp;
char *strdup(const char *s);
/* Checks to see if data exists, consider inserting COUNT here */
for(tmp = hashtable[i]; tmp != NULL; tmp = tmp->next) {
if(tmp->data != 0) { /* root node */
int count = tmp->count;
if(!strcmp(data, tmp->data))
count= count+1;
tmp->count = count;
return;
}
}
for(tmp = hashtable[i]; tmp->next != NULL; tmp = tmp->next);
if(tmp->next == NULL) {
tmp->next = h_alloc();
tmp = tmp->next;
tmp->data = strdup(data);
tmp->next = NULL;
tmp->count = 1;
} else
exit(EXIT_FAILURE);
}
/* Hash function, takes value (string) and converts into an index into the array of linked lists) */
unsigned int h_assign(char *string)
{
unsigned int num = 0;
while(*string++ != '\0')
num += *string;
return num % H_SIZE;
}
/* h_initialize(void) initializes the array of linked lists. Allocates one node for each list by calling h_alloc which creates a new node and sets node.next to null */
void h_initialize(void)
{ int i;
for(i = 0; i <H_SIZE; i++) {
hashtable[i] = h_alloc();
}
}
/* h_alloc(void) is a method which creates a new node and sets it's pointer to null */
struct node *h_alloc(void)
{
struct node *tmp = calloc(1, sizeof(struct node));
if (tmp != NULL){
tmp->next = NULL;
return tmp;
}
else{
exit(EXIT_FAILURE);
}
}
/* Clean up hashtable and free up memory */
void h_free(void)
{
struct node *tmp;
struct node *fwd;
int x;
for(x = 0; x < H_SIZE; x++) {
tmp = hashtable[x];
while(tmp != NULL) {
fwd = tmp->next;
free(tmp->data);
free(tmp);
tmp = fwd;
}
}
}