关于结构体指针问题。
typedef struct data{
char c;
int freq;
int code;
int size;
} Data;
typedef struct node
{
void* data;
struct node* prev;
struct node* next;
struct node* parent;
struct node* lchild;
struct node* rchild;
} Node;
Node* cur = NULL;
for (cur = list->head->next; cur != list->head; cur = cur->next)
printf("(%c %d) ",
((Data*)cur->data)->c,
((Data*)cur->data)->freq);//这一句表示什么含义（我没把整个函数代码写全）
for (cur = list->head->next; cur != list->head && ((Data*)cur->data)->freq < data->freq; cur = cur->next) // 或者是(（Date*）cur->data)->freq < data -> freq 是什么意思
;
