c04p201.txt

Data Abstraction & Problem Solving with C++源码

// Creates a linked list from the data in a text 
// file. The pointer variables head and tail are
// initially NULL. fileName is a string that names
// an existing external text file.

ifstream inFile(fileName);
int      nextItem;

if (inFile >> nextItem)               // is file empty?
{  // file not empty:
   head = new Node;
   // add the first integer to the list
   head->item = nextItem;
   head->next = NULL;
   tail = head;

   // add remaining integers to linked list
   while (inFile >> nextItem)
   {  tail->next = new Node;
      tail = tail->next;
      tail->item = nextItem;
      tail->next = NULL;
   }  // end while
}  w// end if

inFile.close();

// Assertion: head points to the first node of the
// created linked list; tail points to the last
// node. If the file is empty, head and tail are
// NULL (list is empty).