复制并排序链接列表

Question

I have a linked list of Nodes, each Node is defined as:

struct Node {
  char name[14];
  int counts[130];
  char gender;
  Node *nextPtr;
};

I am copying this linked list with the following code:

// Create a copy of the current list
  Node *tempPtr;
  while (headPtr != NULL) {
    tempPtr = new Node;
    tempPtr = headPtr;

    // Advance the list
    headPtr = headPtr->nextPtr;
  } // End while loop

I need to copy the list so that I can sort it, I do not want to sort the original list. The sorting will be descending based on a value at a certain position of the counts[] array. I am wondering is somebody could tell me, am I copying the list correctly? And if I can have some insight as to how to go about and sort this list. I have written this in Java with no problem, I apologize for knowing too little of the c programming language. Any input will be greatly appreciated. Thank you.

My apologies, I am to write this in the c++ programming language. However, I am not allowed to use C++ classes. I can only use C++ I/O stream, reference parameters, and dynamic memory allocation.

My main goal here is to make a list of pointers to the existing nodes, and then sort it without copying the nodes or disturbing the original list.

Answer 1

There's no such thing as new in C. Are you using a c++ compiler?

Ignoring that, the problem is you aren't copying anything, and in fact are creating a memory leak:

tempPtr = new Node;
tempPtr = headPtr;

You create a new node on the heap, assigning the pointer to tempPtr ... then reassign tempPtr to headPtr . You just lost that newly allocated Node (memory leak).

To make a copy of the list, you need to iterate through your existing list, copying the data into new nodes that you're adding to a new list.

Node *oldNode = headPtr;
Node *newHead = malloc(sizeof(struct Node));
Node *tail = newHead;

while(oldNode != NULL)
{
    memcpy(tail, oldNode, sizeof(struct Node));
    oldNode = oldNode->nextPtr;
    if (oldNode != NULL)
    {
        tail->nextPtr = malloc(sizeof(struct Node));
        tail = tail->nextPtr;
    }
}

(untested and I've not done C for a while but that should do it)