Question

编译正常但在执行时我得到分段错误（核心转储）错误。我已经单独测试了每个功能，并且添加功能是唯一一个给我这个错误的功能。添加函数应该将值添加到链表的头部。运行代码时，值会正确添加到列表中，我可以显示列表，但错误发生在不久之后。非常感谢任何帮助！

 //Homework 11
 //Linked List

 #include <iostream>
 using namespace std;

 //Declaring class and Linked List.
 class NumberList
 {
 private:

   struct ListNode
   { 
    double value;
    struct ListNode *next;
   };

   ListNode *head;

 public:

    NumberList()
     { head = NULL;}

    ~NumberList()
     { 
      ListNode *nodePtr;
      ListNode *nextNode;
      nodePtr = head;

      while (nodePtr != NULL)
       {
       nextNode = nodePtr->next;
   delete nodePtr;
   nodePtr = nextNode;
     }
   }

 //Function inserting node at the head.
 void add(double x)
 {
 ListNode *newNode;
 ListNode *nodePtr;
 ListNode *previousNode = NULL;

  newNode = new ListNode;
  newNode->value = x;

 if (!head) 
  {
  head = newNode;
  newNode -> next = NULL;
 }
 else
 {
  nodePtr = head;
  previousNode = NULL;
  }  
  if (previousNode == NULL)
 {   
 head = newNode;
 newNode->next = nodePtr;
 }


 }

 //Function to find matching values.
 bool isMember(double x)
 {
 int pos = 0;
 bool flag = false;

 if (head == NULL)
 {
 cout << "List is Empty" << endl;
 return flag;
 }

ListNode *nodePtr;

 nodePtr = head;

while (nodePtr != NULL)
{
pos++;
if (nodePtr->value == x)
{
  flag = true;
  cout << x << " was found at position " << pos << endl;
}
nodePtr = nodePtr->next;
}

 if (!flag)
  {
    cout << x << " not found in the list." << endl;
  }
 return flag;
 }

 //Function to display linked list values.
 void display() const
 {
   ListNode *nodePtr;

 if (head == NULL)
  {
 cout << "List is empty." << endl;
 return;
  }

  nodePtr = head;

   cout << "The list goes: " << endl;

  while (nodePtr != NULL)
  {
  cout << nodePtr->value << endl;
  nodePtr = nodePtr->next;
  }

   cout << "End" << endl;
  }

  //Function to delete a selected value in the list.
  void deletNodeAll(double x1)
  {
  ListNode *nodePtr;
  ListNode *previousNode;

  if (!head)
  return;

  if (head->value == x1)
  {
  nodePtr = head->next;
  delete head;
  head = nodePtr;
  }
  else
  {
  nodePtr = head;

  while ( nodePtr != NULL && nodePtr->value != x1)
  {
   previousNode = nodePtr;
   nodePtr = nodePtr->next;
  }

   if (nodePtr)
  { 
    previousNode->next = nodePtr->next;
    delete nodePtr;
  }
  }
 }
 };

 int main()
 {
   NumberList Z;

   Z.add(3);
   Z.add(4);
   Z.add(2);
   Z.add(5);
   Z.add(7);
   Z.add(4);
   Z.add(7);
   Z.add(5);
   Z.add(2);
   Z.display();
   Z.isMember(2);
   Z.deletNodeAll(2);
   Z.display();

 return 0;
 }

Answer 1

您的add()方法导致细分错误，因为对于第一个节点，您应该更新head和head->next以及return，但您没有。

if (!head) {
    head = newNode;                            
    newNode -> next = NULL;                           
    return ;/* do this else this again check previousNode == NULL also
                        which is not needed 1st time */  
}

此外deletNodeAll()仅删除您传递的第一个号码，逻辑中存在错误，请自行检查。

插入功能，分段故障（核心转储）中的链接列表错误

1 个答案: