Question

我对C很新，并且正在尝试在C中实现链表。在代码中应该将节点添加到空链表或将节点插入列表开头的部分，后者但是在尝试将单个节点添加到空链表时会发生错误。其余的程序运行正常。

编辑：我在在线GDB调试器上运行代码，它在第111行显示错误。如果我删除了该代码块，它不再抛出错误。但是，我仍然无法弄清楚为什么会在那里抛出错误。

分段错误。
在main.c：111的AddAfter（）中的0x0000000000400927 111 while（prevNode-＆gt; next！= NULL）

以下是my code的详细信息。

/*
# main() is at the bottom.

*/


#include <stdio.h>
#include <stdlib.h>
#include <Windows.h>

typedef struct node
{
  int data;
  struct node * next;
} node;

//Global Variable
node* head = NULL;


node* createList()
{
 int n;
 printf("Loading...\n");
 Sleep(1);
 printf("How many nodes would you like to have in the list ?\n");
 scanf("%d",&n);

 int i;
 node* temp = NULL;
 node* nodeJumper = NULL;

 for (i = 0; i<n; i++)
 {
   temp = malloc(sizeof(node));
   printf("Enter node %d : ",i+1);
   scanf("%d", &(temp->data));
   temp->next = NULL;

   if (head == NULL)
     head = temp;

   else
   {
     nodeJumper = head;
     while (nodeJumper->next != NULL)
        nodeJumper = nodeJumper -> next;
     nodeJumper->next = temp;
   }
 }
 printf("Sucessfully created\n\n");
 return head;
}


void printList()
{
 node* nodeptr = NULL;
 if (head == NULL)
    printf("The list is empty.");
 else
   {
    nodeptr = head;
    printf("Your Linked List : ");
    while(nodeptr != NULL)
      {
        printf(" %d>", nodeptr->data);
        nodeptr = nodeptr->next;
      }
    printf("\n\n");
    }

}


int countNode()
{
 node* temp = head;
 int count = 0;
 while (temp!= NULL)
  { count++;
    temp = temp-> next;
  }
 return count;
}


void AddAfter()
{
 int pos, data;
 printf("Loading...\n");
 Sleep(1);
 printf("Enter position number to insert new node: ");
 scanf("%d",&pos);

 printf("Enter a number to enter in the list: ");
 scanf("%d", &data);


 int count = countNode(); //Count no. of nodes in linked list
 int i;
 node* prevNode = head; //node before inserted new node.

 node* temp = malloc(sizeof(node));
 temp->data = data;



  if (pos == count+1) //Append the list
  {
   while (prevNode->next != NULL)
      prevNode= prevNode->next;
   temp->next = NULL;
   prevNode->next = temp;
  }

  else if (pos == 1) //Throws error while trying to add node to empty linked list
  {
   temp->next = head;
   head = temp;
  }

  else if (pos <= count && pos >= 1)
  {
   for (i=1; i< pos-1; i++)
     prevNode = prevNode->next;
   temp->next = prevNode->next;
   prevNode->next = temp;
  }
  else //Invalid positions input by user.
  {
   printf("Request unsucessful\n");
   printf("Only positions 1 to %d are valid", count+1);
  }

}


int printMenu()
{
 int option;
 printf("Select options from menu:\n");
 printf("1> Create Linked List\n2> Add nodes anywhere in the linked list\n3> Quit\n\n");
 printf("Enter option number here: ");

 scanf("%d",&option);
 return option;
}


int main()
{
 printf("\n\t### Welcome to Linked list manager ###\n\n");

 while(1)
 {
   int userChoice = printMenu();

   if (userChoice == 1)
   {
    head = createList();
    printList();
   }


   else if (userChoice == 2)
   {
    AddAfter();
    printf("\n");
    printList();
   }

   else if (userChoice ==3)
   {
    exit(0);
   }

   else
   {
    printf("Enter a valid option number.\n");
   }
 }

return 0;
}

我一直想弄清楚几个小时。任何指导都将非常感谢。

Answer 1

只是一个下意识的反应，如果＆＃34; prevNode＆＃34;会发生什么？是无效还是NULL？如果你运行＆＃34;选项2＆＃34;在运行＆＃34;选项1＆＃34;之前，＆＃34; head＆＃34;将为NULL，并且您将进行segv。您应该添加一个签入＆＃34; AddAfter＆＃34;验证＆＃34; head＆＃34;不是NULL。

为什么我的代码在这个C代码中抛出错误？

1 个答案: