why i get this error when i try to scroll through a list to its last element?-CodePudding

Im trying to resolve the 21. Merge Two Sorted Lists on leetCode. The problem is composed as follows: I have two linked lists already ordered in ascending order and I have to combine them into a single list that is also ordered in ascending order.

This is my code:

struct ListNode *sortList(struct ListNode *headList) {
    struct ListNode *ptrHead = headList;
    int temp;
    if(headList == NULL)
    return NULL;

    while(ptrHead->next != NULL){
        if(ptrHead->val > ptrHead->next->val){
            temp = ptrHead->val;
            ptrHead->val = ptrHead->next->val;
            ptrHead->next->val = temp;
            ptrHead = headList;
        }else{
            ptrHead = ptrHead->next;
        }
    }

    return headList;
}

void addNode(struct ListNode **list, int data){
      struct ListNode *newNode = (struct ListNode *) malloc(sizeof (struct ListNode)), *temp = NULL;

      if((*list) == NULL){
          newNode->val = data;
          newNode->next = NULL;
          (*list) = newNode;
      }else{
          temp = (*list);
          while (temp->next != NULL){
              temp = temp->next;
          }
          newNode->val = data;
          temp->next = newNode;
      }
}

struct ListNode *mergeTwoLists(struct ListNode *l1, struct ListNode *l2){
    struct ListNode *newList = NULL;

    while (l1 != NULL){
        addNode(&newList, l1->val);
        l1 = l1->next;
    }
    while (l2 != NULL){
        addNode(&newList, l2->val);
        l2 = l2->next;
    }

    return sortList(newList);
}

I tried to run it locally and I had no problem but when I go to run it on the leet code I get an error

The error:

    Line 19: Char 20: runtime error: member access within misaligned address 
    0xbebebebebebebebe for type 'struct ListNode', which requires 8 byte alignment 
    [solution.c]
    0xbebebebebebebebe: note: pointer points here
    <memory cannot be printed>

CodePudding user response：

The function addNode has a bug. You forgot to set the data member next to NULL in this code snippet

  }else{
      temp = (*list);
      while (temp->next != NULL){
          temp = temp->next;
      }
      newNode->val = data;
      temp->next = newNode;
  }

You need to write at least

  }else{
      temp = (*list);
      while (temp->next != NULL){
          temp = temp->next;
      }
      newNode->val = data;
      newNode->Next = NULL;
      temp->next = newNode;
  }

The reason of the error is a duplicated code. I would define the function the following way

int addNode( List **list, int data )
{
    struct ListNode *newNode = malloc( sizeof ( *newNode ) );
    int success = newNode != NULL;

    if ( success )
    {
        newNode->val  = data;
        newNode->next = NULL;

        while ( *list ) list = &( *list )->next;
        *list = newNode;
    }

    return success;
}

Pay attention to that using two different names for the same entity like List and struct ListNode confuses readers of the code.

And to merge two lists there is no need to create copies of the lists as you are doing in the function mergeTwoLists.