I want to delete the front node in delete_first
.
Here is the code:
#include <stdio.h>
#include <stdlib.h>
typedef int element;
typedef struct DListNode {
element data;
struct DListNode *llink;
struct DListNode *rlink;
} DlistNode;
void init(DListNode *phead) {
phead->llink = phead;
phead->rlink = phead;
}
An error occurs in the part below when I debug.
void print_dlist(DListNode *phead) {
DListNode *p;
for (p = phead->rlink; p != phead; p = p->rlink) {
printf("<-| |%d| |->", p->data);
}
printf("\n");
}
This is my insert code and I think it is not problem
void dinsert(DListNode *before, element data) {
DListNode *newnode = (DListNode *)malloc(sizeof(DListNode));
newnode->data = data;
newnode->llink = before;
newnode->rlink = before->rlink;
before->rlink->llink = newnode;
before->rlink = newnode;
}
I want to fix some error in that delete_first
code but I don't know what is the problem and how to fix it.
void delete_first(DListNode *head) {
head = head->rlink;
if (head != NULL) {
head->llink = NULL;
}
free(head);
}
int main() {
DListNode *head = (DListNode *)malloc(sizeof(DListNode));
init(head);
printf("insert\n");
for (int i = 0; i < 5; i++) {
dinsert(head, i);
print_dlist(head);
}
printf("\n delete \n");
delete_first(head);
print_dlist(head);
free(head);
return 0;
}
How can I delete my front node using the head
node?
To delete the first node of the doubly linked list, you must free the node pointed to by head->rlink
unless head->rlink
points to head
itself, which is the case if the list is empty:
void delete_first(DListNode *head) {
DListNode *p = head->rlink;
if (p != head) {
p->llink->rlink = p->rlink;
p->rlink->llink = p->llink;
free(head);
}
}
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