我必须复制和扩展数据结构类的一些代码。它是作为 ADT 的链表模板。我遇到了一些错误，但是在花了几个小时研究它们是什么并梳理我的代码之后，我一生都无法弄清楚我错过了什么。我见过其他人发布了同样的错误，但看看他们的代码出了什么问题，我似乎没有这些问题 - 或者如果我有，我完全忽略了它。
所以这里是 .h、.cpp 和 main，后跟确切的错误：
#ifndef nodeType_h
#define nodeType_h
template<class Type>
struct nodeType
{
Type info;
nodeType<Type> *link;
};
#endif /* nodeType_h */
#ifndef LinkedList_h
#define LinkedList_h
#include "LinkedListIterator.h"
#include "nodeType.h"
template <class Type>
class LinkedList
{
public:
const LinkedList<Type>& operator=(const LinkedList<Type>&);
// Function to overload the assignment operator.
void initializeList();
// Function to initialize like to an empty state.
// Precondition: A full list is passed for clearing.
// Postcondition: first = NULL, last = NULL, count = 0;
bool isEmptyList() const;
// Function to determine whether or not the list is empty.
// Precondition:
// Postcondition: Returns true if the list is empty, false otherwise.
void print() const;
// Function to display data in each node.
// Precondition: Function is called.
// Postcondition: None.
int length() const;
// Function to return the number of nodes in the list.
// Precondition:
// Postcondition: The value of count is returned.
void destroyList();
// Function to delete all the nodes from the list.
// Precondition:
// Postcondition: first = NULL, last = NULL, count = 0;
Type front() const;
// Function to return the first element of the list.
// Precondition: The list must exist and must not be empty.
// Postcondition: If the list is empty, the program terminates. Otherwise,
// the first element of the list is returned.
Type back() const;
// Function to return the last element of the list.
// Precondition: The list must exist and must not be empty.
// Postcondition: If the list is empty, the program terminates. Otherwise,
// the last element of the list is returned.
virtual bool search(const Type& searchItem) const = 0;
// Function to determine whether or not the searchItem is in the list.
// Precondition:
// Postcondition: Returns true if searchItem is in the list, false otherwise.
virtual void insertFirst(const Type& newItem) = 0;
// Function to insert newItem at the beginning of the list.
// Precondition:
// Postcondition: first points to the new list, newItem is inserted at the
// beginning of the list, last points to the last node in the
// list, and count is incremented by 1.
virtual void insertLast(const Type& newItem) = 0;
// Function to insert newItem at the beginning of the list.
// Precondition:
// Postcondition: first points to the new list, newItem is inserted at the
// end of the list, last points to the last node in the
// list, and count is incremented by 1.
virtual void deleteNode(const Type& deleteItem) = 0;
// Function to delete deleteItem from the list.
// Precondition:
// Postcondition: If found, the node containing deleteItem is deleted from
// the list. first points to the first node, last points to the
// last node of the updated list, and coint is decremented by 1.
LinkedListIterator<Type> begin();
// Function to return an iterator at the beginning of the linked list.
// Precondition:
// Postcondition: Returns an iterator such that current is set to first.
LinkedListIterator<Type> end();
// Function to return an iterator one element past the last element of the linked list.
// Precondition:
// Postcondition: Returns an iterator such that current is set to NULL.
LinkedList();
// Default constructor initializes list to an empty state.
// Precondition:
// Postcondition: first = NULL, last = NULL, count = 0;
LinkedList(const LinkedList<Type>& otherList);
// Copy constructor.
~LinkedList();
// Destructor deletes all the nodes from the list.
// Precondition:
// Postcondition: The list object is destoryed.
protected:
int count; // Variable to store the number of list elements.
nodeType<Type> *first; // Pointer to the first node of the list.
nodeType<Type> *last; // Pointer to the last node of the list.
private:
void copyList(const LinkedList<Type>& otherList);
// Function to make copy of otherList.
// Postcondition: A copy of otherList is created and assigned to the list.
};
#endif /* LinkedList_h */
#include "LinkedList.h"
#include "LinkedListIterator.h"
#include "nodeType.h"
#include <iostream>
template <class Type>
const LinkedList<Type>& LinkedList<Type>::operator=(const LinkedList<Type>& otherList)
{
if(this != otherList) // Avoid self-copy.
{
copyList(otherList);
}
return *this;
}
template <class Type>
void LinkedList<Type>::initializeList()
{
destroyList(); // If the list has any nodes, delete them.
}
template <class Type>
bool LinkedList<Type>::isEmptyList() const
{
return first == NULL;
}
template <class Type>
void LinkedList<Type>::print() const
{
nodeType<Type> *current; // Pointer to traverse the list.
current = first; // Point current to the first node.
while(current != NULL) // While there is data to print.
{
std::cout << current->info << " ";
current = current->link;
}
}
template <class Type>
int LinkedList<Type>::length() const
{
return count;
}
template <class Type>
void LinkedList<Type>::destroyList()
{
nodeType<Type> *temp; // Pointer to deallocate memory occupied by the node.
while(first != NULL) // While there are nodes in the list.
{
temp = first; // Set temp to current node.
first = first->link; // Advance first to the next node.
delete temp; // Deallocate memory occupied by temp.
}
last = nullptr; // Initialize last to NULL.
count = 0; // Set count to 0.
}
template <class Type>
Type LinkedList<Type>::front() const
{
assert(first != NULL);
return first->info; // Return the info of the first node.
}
template <class Type>
Type LinkedList<Type>::back() const
{
assert(last != NULL);
return last->info; // Return the info of the last node.
}
template <class Type>
bool LinkedList<Type>::search(const Type& searchItem) const
{
}
template <class Type>
void LinkedList<Type>::insertFirst(const Type& newItem)
{
}
template <class Type>
void LinkedList<Type>::insertLast(const Type& newItem)
{
}
template <class Type>
void LinkedList<Type>::deleteNode(const Type& deleteItem)
{
}
template <class Type>
LinkedListIterator<Type> LinkedList<Type>::begin()
{
LinkedListIterator<Type> temp(first);
return temp;
}
template <class Type>
LinkedListIterator<Type> LinkedList<Type>::end()
{
LinkedListIterator<Type> temp(NULL);
return temp;
}
template <class Type>
LinkedList<Type>::LinkedList()
{
first = NULL;
last = NULL;
count = 0;
}
template <class Type>
LinkedList<Type>::LinkedList(const LinkedList<Type>& otherList)
{
first = NULL;
copyList(otherList);
}
template <class Type>
LinkedList<Type>::~LinkedList()
{
destroyList();
}
template <class Type>
void LinkedList<Type>::copyList(const LinkedList<Type>& otherList)
{
nodeType<Type> *newNode; // Pointer to create a node.
nodeType<Type> *currentNode; // Pointer to traverse the list.
if(first != NULL) // If the list is not empty, empty it.
{
destroyList();
}
if(otherList.first == NULL) // If otherList is empty.
{
first = NULL;
last = NULL;
count = 0;
}
else
{
currentNode = otherList.first; // currentNode points to the list to be copied.
count = otherList.count;
// Copy the first node.
first = new nodeType<Type>; // Create the node.
first->info = currentNode->info; // Copy the info.
first->link = NULL; // Set link to NULL.
last = first; // Make last point to first node.
currentNode = currentNode->link; // Make currentNode point to the next node.
// Copy the rest of the list.
while(currentNode != NULL)
{
newNode = new nodeType<Type>; // Create a new node.
newNode = currentNode->info; // Copy the info.
newNode->link = NULL; // Set newNode link to NULL.
last->link = newNode; // Attach newNode to end of list.
last = newNode; // Make last point to last node.
currentNode = currentNode->link; // Make currentNode point to the next node.
}
}
}
#ifndef LinkedListIterator_h
#define LinkedListIterator_h
#include "nodeType.h"
template<class Type>
class LinkedListIterator
{
public:
LinkedListIterator();
// Default constructor.
// Precondition:
// Postcondition: current = NULL;
LinkedListIterator(nodeType<Type> *ptr);
// Constructor that accepts a nodeType object and points current to it.
// Precondition:
// Postcondition: current = ptr;
Type operator*();
// Function to overload the dereferencing operator *.
// Precondition:
// Postcondition: Returns the info contained in the node.
LinkedListIterator<Type> operator++();
// Function to overload the preincrement operator.
// Precondition:
// Postcondition: The iterator is advanced to the next node.
bool operator==(const LinkedListIterator<Type>& right) const;
// Function to overload the equality operator.
// Precondition:
// Postcondition: Returns true if this iterator is equal to the iterator
// specified by the right, false otherwise.
bool operator!=(const LinkedListIterator<Type>& right) const;
// Function to overload the not equal to operator.
// Precondition:
// Postcondition: Returns true if this iterator is not equal to the iterator
// specified by the right, false otherwise.
private:
nodeType<Type> *currentNode; // Pointer to point to the current node in the list.
};
#endif /* LinkedListIterator_h */
#include "LinkedListIterator.h"
#include <iostream>
template <class Type>
LinkedListIterator<Type>::LinkedListIterator()
{
currentNode = NULL;
}
template <class Type>
LinkedListIterator<Type>::LinkedListIterator(nodeType<Type> *ptr)
{
currentNode = ptr;
}
template <class Type>
Type LinkedListIterator<Type>::operator*()
{
return currentNode->info;
}
template <class Type>
LinkedListIterator<Type> LinkedListIterator<Type>::operator++()
{
currentNode = currentNode->link;
}
template <class Type>
bool LinkedListIterator<Type>::operator==(const LinkedListIterator<Type> &right) const
{
return (currentNode == right.currentNode);
}
template <class Type>
bool LinkedListIterator<Type>::operator!=(const LinkedListIterator<Type> &right) const
{
return (currentNode != right.currentNode);
}
#ifndef UnorderedLinkedList_h
#define UnorderedLinkedList_h
#include "LinkedList.h"
#include "nodeType.h"
#include <iostream>
template <class Type>
class UnorderedLinkedList: public LinkedList<Type>
{
public:
bool search(const Type& searchItem) const;
// Function to determine whether or not the searchItem is in the list.
// Precondition:
// Postcondition: Returns true if searchItem is in the list, false otherwise.
void insertFirst(const Type& newItem);
// Function to insert newItem at the beginning of the list.
// Precondition:
// Postcondition: first points to the new list, newItem is inserted at the
// beginning of the list, last points to the last node in the
// list, and count is incremented by 1.
void insertLast(const Type& newItem);
// Function to insert newItem at the beginning of the list.
// Precondition:
// Postcondition: first points to the new list, newItem is inserted at the
// end of the list, last points to the last node in the
// list, and count is incremented by 1.
void deleteNode(const Type& deleteItem);
// Function to delete deleteItem from the list.
// Precondition:
// Postcondition: If found, the node containing deleteItem is deleted from
// the list. first points to the first node, last points to the
// last node of the updated list, and coint is decremented by 1.
};
#endif /* UnorderedLinkedList_h */
#include <stdio.h>
#include "UnorderedLinkedList.h"
template <class Type>
bool UnorderedLinkedList<Type>::search(const Type &searchItem) const
{
nodeType<Type> *currentNode; // Pointer to traverse the list.
bool found = false;
currentNode = LinkedList<Type>::first; // Set currentNode to point to the first node in the list.
while(currentNode != NULL && !found) // Search the list.
{
if(currentNode->info == searchItem) // If seachItem is found.
{
found = true;
}
else
{
currentNode = currentNode->link; // Makes current point to the next node.
}
}
}
template <class Type>
void UnorderedLinkedList<Type>::insertFirst(const Type &newItem)
{
nodeType<Type> *newNode; // Pointer to create the new node.
newNode = new nodeType<Type>; // Create the new node.
newNode->info = newItem; // Store the new item in the node.
newNode->link = LinkedList<Type>::first; // Insert newNode before first.
LinkedList<Type>::first = newNode; // Make first point to the actual first node.
LinkedList<Type>::count++; // Increment count.
if(LinkedList<Type>::last == NULL) // If the list was empty, newNode is also the last node.
{
LinkedList<Type>::last = newNode;
}
}
template <class Type>
void UnorderedLinkedList<Type>::insertLast(const Type &newItem)
{
nodeType<Type> *newNode; // Pointer to create the new node.
newNode = new nodeType<Type>; // Create the new node.
newNode->info = newItem; // Store the new item in the node.
newNode->link = NULL; // Set the link of newNode to NULL.
if(LinkedList<Type>::first == NULL) // If the list is empty, insert newNode after last.
{
LinkedList<Type>::first = newNode;
LinkedList<Type>::last = newNode;
LinkedList<Type>::count++; // Increment count.
}
else
{
LinkedList<Type>::last->link = newNode; // Insert newNode after last.
LinkedList<Type>::last = newNode; // Make last point to the actual last node in the list.
LinkedList<Type>::count++; // Increment count.
}
}
template <class Type>
void UnorderedLinkedList<Type>::deleteNode(const Type &deleteItem)
{
nodeType<Type> *currentNode; // Pointer for traversing the list.
nodeType<Type> *trailCurrent; // Pointer just before current.
bool found;
if(LinkedList<Type>::first == NULL)
{
std::cout << "Cannot delete from an empty list.n";
}
else
{
if(this->first->info == deleteItem)
{
currentNode = LinkedList<Type>::first;
LinkedList<Type>::first = LinkedList<Type>::first->link;
LinkedList<Type>::count++;
if(LinkedList<Type>::first == NULL)
{
LinkedList<Type>::last = NULL;
}
delete currentNode;
}
else // Search the list for the node with the given info.
{
found = false;
trailCurrent = LinkedList<Type>::first; // Set trailCurrent to point to the first node.
currentNode = LinkedList<Type>::first->link; // Set currentNode to point to the second node.
while(currentNode != NULL && !found)
{
if(currentNode->info != deleteItem)
{
trailCurrent = currentNode;
currentNode = currentNode->link;
}
else
{
found = true;
}
}
if(found) // If found, delete the node.
{
trailCurrent->link = currentNode->link;
LinkedList<Type>::count--;
if(LinkedList<Type>::ast == currentNode) // Node to be deleted was the last node.
{
LinkedList<Type>::last = trailCurrent; // Update the value of last.
}
delete currentNode; // Delete the node from the list.
}
else
{
std::cout << "The item to be deleted is not in the list.n";
}
}
}
}
#include <iostream>
#include "stdio.h"
#include "UnorderedLinkedList.h"
int main()
{
UnorderedLinkedList<int> list1, list2;
int num;
for(int i = 0; i < 10; i++)
{
std::cout << "Enter a number: ";
std::cin >> num;
std::cout << std::endl;
if(i == 0)
{
list1.insertFirst(num);
}
else
{
list1.insertLast(num);
}
}
list1.print();
return 0;
}
错误：
Undefined symbols for architecture x86_64:
"LinkedList<int>::LinkedList()", referenced from:
UnorderedLinkedList<int>::UnorderedLinkedList() in main.o
"LinkedList<int>::~LinkedList()", referenced from:
UnorderedLinkedList<int>::~UnorderedLinkedList() in main.o
"UnorderedLinkedList<int>::deleteNode(int const&)", referenced from:
vtable for UnorderedLinkedList<int> in main.o
"UnorderedLinkedList<int>::insertLast(int const&)", referenced from:
_main in main.o
vtable for UnorderedLinkedList<int> in main.o
"UnorderedLinkedList<int>::insertFirst(int const&)", referenced from:
_main in main.o
vtable for UnorderedLinkedList<int> in main.o
"LinkedList<int>::print() const", referenced from:
_main in main.o
"UnorderedLinkedList<int>::search(int const&) const", referenced from:
vtable for UnorderedLinkedList<int> in main.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
我从教科书上复制了上面的代码，除了主要的。主要不是从教科书中复制的，尽管它也可能是。我只是想在对家庭作业进行所需的更改之前让它工作，但它没有发生。任何意见将不胜感激。谢谢。
问题解决了，尽管我仍然不知道代码出了什么问题。两位教授看了看，看不出有什么不对劲的地方，最终，我得知源代码是可用的。我下载了它并将其与我所拥有的进行了比较。它是相同的，只是它在头文件中包含了实现代码，这应该没有区别。无论如何，这不再是问题。