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c - 删除双循环链表中节点的正确方法

问题描述

此代码的目的是管理插入和删除以及可视化。我只想知道我是否正确地做所有事情，让我知道是否有更多可能的方法来做到这一点。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;
}

我如何测试这是否是一个真正的循环双向链表而不是一个简单的双向链表？

标签： cnodesdoubly-linked-listcircular-list

解决方案

您的程序运行良好，我检测到的唯一真正的错误是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了函数的开头，这意味着您要搜索的元素不在列表中：

修正版：

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，不会阻止程序正常工作：

其中之一是：该n变量不在外部使用ReadData，因此在其中声明它main并将其指针传递给ReadData.

修正版：

void ReadData(Node * head)
{
  int n;  // declare n locally
  printf("\nInsert a number:");
  scanf("%d", &n);
  NewNode(head, n);
}

像这样称呼它：ReadData(&head)并int n;从main.

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