[英]Correct way to delete a node in doubly circular linked list
此代码的目的是管理插入,删除和可视化。 我只是想知道我是否做得正确,请告诉我是否还有更多可行的方法。 这是我的第一次尝试,我没有遵循任何教程。
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct Node {
int n;
struct Node *next;
struct Node *prev;
}TNode;
typedef TNode* Node;
void NewNode(Node *pp, int n)
{
Node temp, last;
temp = (Node)malloc(sizeof(struct Node));
temp->n = n;
temp->next = temp;
temp->prev = temp;
if(*pp != NULL)
{
last = (*pp)->prev;
temp->next = (*pp);
temp->prev = last;
last->next = (*pp)->prev = temp;
}
*pp = temp;
}
void ViewList(Node head)
{
if(head == NULL)
{
return;
}
Node node = head->prev;
do
{
printf("Curr: %d\n", node->n);
node = node->prev;
}while(node != head->prev);
}
void ReadData(Node * head, int * n)
{
printf("\nInsert a number:");
scanf("%d", n);
NewNode(head, *n);
}
Node SearchNode(Node head)
{
int d;
printf("\nElement to Delete:");
scanf("%d", &d);
while(head != NULL)
{
if(head->n == d)
{
return head;
}
head = head->next;
}
printf("\nNo Element [%d] Found", d);
return NULL;
}
void Delete(Node * head)
{
Node del = SearchNode(*head);
if(*head == NULL || del == NULL)
{
return;
}
if(*head == del && del->next == *head)
{
*head = NULL;
free(del);
return;
}
if(*head == del)
{
*head = del->next;
del->prev->next = *head;
(*head)->prev = del->prev;
free(del);
return;
}
if((*head)->prev == del)
{
(*head)->prev = del->prev;
del->prev->next = *head;
free(del);
return;
}
del->next->prev = del->prev;
del->prev->next = del->next;
free(del);
}
int Menu()
{
int c;
printf("\n*** M E N U ***\n"
"1 - New Node\n"
"2 - View List\n"
"3 - Delete\n"
"0 - Exit\n"
"\n>> ");
scanf(" %d", &c);
return c;
}
int main()
{
int c,n;
Node head = NULL;
do {
c = Menu();
switch (c)
{
case 1: ReadData(&head, &n); break;
case 2: ViewList(head); break;
case 3: Delete(&head); break;
default: c = 0;
}
} while (c != 0);
return 0;
}
我如何测试这是一个真正的圆形双向链表,而不是一个简单的双向链表?
您的程序运行良好,我检测到的唯一真正的错误是在SearchNode
:如果列表中不存在该元素,则进入无限循环。 您的列表显然是一个循环列表,因此您需要检查您是否回到函数的开头,这意味着您要搜索的元素不在列表中:
更正的版本:
Node SearchNode(Node head)
{
int d;
printf("\nElement to Delete:");
scanf("%d", &d);
Node start = head; // remember where we started
while (head != NULL)
{
if (head->n == d)
{
return head;
}
head = head->next;
if (head == start) // if we are back to where we started
break; // the element hasn't been found and we stop the loop
}
printf("\nNo Element [%d] Found", d);
return NULL;
}
还有一些设计缺陷,它们不能阻止程序正常工作:
其中之一是:在ReadData
外部不使用n
变量,因此在main
声明该变量并将其指针传递给ReadData
毫无意义。
更正的版本:
void ReadData(Node * head)
{
int n; // declare n locally
printf("\nInsert a number:");
scanf("%d", &n);
NewNode(head, n);
}
这样调用: ReadData(&head)
并删除int n;
从main
。
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