0
这是我如何实现一个队列链接队列。由于add函数工作不正常,我无法测试其他函数,除了似乎正在工作的new_queue外。Dyanmic队列优先,添加功能不起作用
#include <stdlib.h>
struct Qelement {
struct Qelement *next;
int prio;
const char *dataptr;
};
typedef struct Qelement *Queue;
// creates an empty queue
Queue new_queue()
{
Queue q = (Queue)malloc(sizeof(struct Qelement));
q->next = NULL;
q->prio = 0;
q->dataptr = NULL;
return q;
}
// removes the queue and all its elements
void delete_queue (Queue q)
{
Queue tmp;
while (q->next != NULL)
{
tmp = q->next;
free (q);
q = tmp;
}
free(q);
}
// emmpties queue
void clear (Queue q)
{
Queue tmp;
while (q->next != NULL)
{
tmp = q->next;
free (q);
q = tmp;
}
q->next = NULL;
q->prio = 0;
q->dataptr = NULL;
}
// get length of queue
int size (Queue q)
{
Queue orginal = q;
int length = 0;
while (q->next != NULL)
{
++length;
q = q->next;
}
++length;
q = orginal;
return length;
}
// add an element to queue
void add (Queue q, int priority, Datatyp *d)
{
Queue tmp;
Queue previous = q;
Queue element = (Queue)malloc (sizeof(struct Qelement));
element->next = NULL;
element->prio = priority;
element->dataptr = d;
if (priority > previous->prio)
{
tmp = q;
q = element;
element->next = tmp;
}
else
{
if (previous->next != NULL)
{
while (priority <= previous->next->prio)
{
previous = previous->next;
}
previous->next = element;
element->next = previous->next->next;
}
else
{
//previous->next = element;
}
}
}
// return first element
Datatyp *get_first (Queue q)
{
return q->dataptr;
}
// removes first element
void remove_first(Queue q)
{
Queue tmp = q->next;
q = q->next;
free(tmp);
}
int main(int argc, char *argv[]) {
const char *daniel = "Daniel";
const char *lisa = "Lisa";
const char *a[] = {"Kalle", "Olle", "Eva", lisa, "Stina",
"Peter", "Anna", daniel, "Johan", "Maria"};
const int correctOrder1[] = {3, 7, 2, 6, 1, 5, 9, 0, 4, 8 };
const int correctOrder2[] = {5, 4, 7, 3, 6};
Queue q = new_queue();
int i;
for (i=0; i<10; i++) {
add(q, i%4, a[i]);
}
printf("Size = %d\n\n", size(q)); // says 1, should say 10
...
}
最后一个printf,在main函数中是1,所以我认为add部分工作不正常。任何指针?
从'typedef struct Qelement * Queue'这仍然是一个问题?队列已经是一个指向Qelement结构的指针。 – Emz
没关系。当您更改传递给函数的局部变量时,它只会在该函数的范围内发生变化。您需要传递该变量的地址,并在函数内部更改该地址的内存内容。换句话说,调用'func(&q,...)'和'func'里面,设置'* q = ...'。 –
void getWordsFromFile(char ** str){... str [0] = ...; }将工作,我相信,我在另一个函数中使用它,调用getWordsFromFile而不从主函数中引用。我已经传递了一个指针,该函数接受一个指针,它没有本地存储的变量。它已经直接在内存上工作了。 – Emz