[英]Unable to delete first element from circular linked list in c
假設列表中有 3 個元素 (10 20 30)。 現在在第一個刪除元素時刪除 10 個。現在只剩下 20 和 30 個了。 同樣,如果我刪除第一個元素,那么 20 將從列表中刪除。 但是現在如果我嘗試從列表中刪除單獨的元素,即 30,它不會發生。
提前致謝。
#include <stdio.h>
#include <stdlib.h>
typedef struct node {
int data;
struct node *next;
} list;
list *start = NULL;
list *create(list *);
list *display(list *);
list *delete_beg(list *);
int main() {
int n;
printf("1: Create list\n");
printf("2: Display\n");
printf("3: Delete first element\n");
for (;;) {
printf("Enter your choice: ");
scanf("%d", &n);
switch (n) {
case 1:
start = create(start);
printf("\nList created successfully\n");
break;
case 2:
start = display(start);
break;
case 3:
start = delete_beg(start);
break;
default:
printf("Wrong input!!!");
exit(0);
}
}
}
list *create(list *start) {
list *new_node, *ptr;
int num;
printf("Enter data: ");
scanf("%d", &num);
new_node = (list *)malloc(sizeof(list));
new_node->data = num;
if (start == NULL) {
start = new_node;
new_node->next = start;
} else {
ptr = start;
while (ptr->next != start) {
ptr = ptr->next;
}
ptr->next = new_node;
new_node->next = start;
}
return start;
}
list *display(list *start) {
list *ptr;
if (start == NULL) {
printf("Empty list");
return start;
} else {
ptr = start;
while (ptr->next != start) {
printf("%d\n", ptr->data);
ptr = ptr->next;
}
printf("%d\n", ptr->data);
}
return start;
}
list *delete_beg(list *start) {
list *ptr;
if (start == NULL) {
printf("Empty list!!!");
return start;
} else {
ptr = start;
while (ptr->next != start)
ptr = ptr->next;
ptr->next = start->next;
free(start);
start = ptr->next;
return start;
}
}
在函數delete_beg
,當列表只包含一個將被刪除的節點時,指針 start 永遠不會設置為 NULL。
該函數可以通過以下方式定義
list *delete_beg(list *start) {
if (start == NULL) {
printf("Empty list!!!");
return start;
} else {
List *current = start;
List *ptr = start;
while (ptr->next != start)
ptr = ptr->next;
if ( ptr->next == ptr )
{
start = NULL;
}
else
{
start = start->next;
ptr->next = start;
}
free( current );
return start;
}
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.