链表节点上的分段错误

Question

I thought about linked list, but there are segmentation fault. But I don't know, why this code has memory leak...

I just tried

codeblock said, ptr = next; <- this part has segmentation fault.

if(head == NULL)
        {
            head = new Nodes;
            head->r_data = data1;
            head->u_data = data2;
            head->r_node = NULL;
            head->u_node = NULL;
        }
        else
        {
            Nodes *ptr;
            ptr = head;
            Nodes *next;
            next = head->r_node;
            while(ptr != NULL)
            {
                if(ptr->r_data == data1)
                {
                    next = ptr->u_node;
                    while(ptr != NULL)
                    {
                        if(ptr->u_data < data2)
                        {
                            ptr = next;
                            next = ptr->u_node;
                        }
                        else
                        {
                            break;
                        }
                    }
                    break;
                }
                else if(ptr->r_data < data1)
                {
                    ptr = next;
                    next = ptr->r_node;
                }
            }
            ptr->r_data = data1;
            ptr->u_data = data2;
            ptr->r_node = NULL;
            ptr->u_node = NULL;
        }

Answer 1

The problem could be that you're trying to access a memory location that doesn't exist. In situations like this, it's always helpful to first check whether the memory location that you want is access is accessible in the first place. In your case, if would help to add something like:

if(ptr->r_data == data1 && ptr->u_node!=NULL)
   {
    next = ptr->u_node;
    ......

Doing things this way will keep you from falling into segmentation issues.