שפת C/ניהול זיכרון דינאמי/תרגילים: הבדלים בין גרסאות בדף
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שורה 20:
{{מוסתר|הפתרון|2=
<source lang = "c">
#include <stdio.h>
#include <stddef.h>
#include <malloc.h>
struct link_
{
struct link_ *next;
int data;
};
typedef struct link_ link;
struct list_
{
link *head;
link *tail;
unsigned long size;
};
typedef struct list_ list;
/* Constructs a list (prepares it for use). */
void list_ctor(list *list);
/* Destructs a list (after use). */
void list_dtor(list *list);
/* Returns the number of elements in the list. */
unsigned long list_size(const list *list);
/* Pushes new data to the head of the list.
* Returns 0 if the operation succeeded, -1 otherwise. */
int list_push(list *list, int data);
/* Pops (removes) the element at the head of the list.
* Returns the element.
* Don't call if the size of the list is 0. */
int list_pop(list *list);
/* Returns the element at the head of the list.
* Don't call if the size of the list is 0. */
int list_head(const list *list);
void list_ctor(list *list)
{
list->head = NULL;
list->tail= NULL;
list->size = 0;
}
void list_dtor(list *list)
{
link *l = list->head;
while(l != NULL)
{
link *const old = l;
l = old->next;
free(old);
}
list_ctor(list);
}
unsigned long list_size(const list *list)
{
return list->size;
}
int list_push(list *list, int data)
{
link *const l = (link *)malloc(sizeof(link));
if(l == NULL)
return -1;
l->data = data;
l->next = NULL;//putting it at end
if(list->size==0)
{
list->head = l;
}
if(list->tail)//not null
{
list->tail->next = l;//keeping the links
}
list->tail = l;
++list->size;
return 0;
}
int list_pop(list *list)
{
link *const l = list->head;
const int data = l->data;
list->head = l->next;
--list->size;
if(!list->size)
{
list->tail=list->head;
}
free(l);
return data;
}
int list_head(const list *list)
{
const link *const l = list->head;
return l->data;
}
int main()
{
int c;
list lst;
list_ctor(&lst);
do
{
int d;
printf("Please enter a number: ");
scanf("%d", &d);
list_push(&lst, d);
printf("Please enter 0 to quit, or any other number to continue: ");
scanf("%d", &c);
}
while(c != 0);
printf("The numbers you entered, in reverse order, are:\n");
while(list_size(&lst) > 0)
printf("%d\n", list_pop(&lst));
list_dtor(&lst);
return 0;
}
}
</source>
}}
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