我正在尝试使用unique_ptr实现单个链表的插入位置函数。我在网上遵循了一个类似的实现，它使用shared_ptr，但我无法使我的功能正常工作，我得到了一个我不太理解的错误：
1>------ Build started: Project: LinkedList, Configuration: Debug Win32 ------
1>main.cpp
1>c:devlinkedlistlinkedlistsinglelinkedlist.h(177): error C2065: 'loc': undeclared identifier
1>c:devlinkedlistlinkedlistsinglelinkedlist.h(168): note: while compiling class template member function 'void SingleLinkedList<int>::insertPosition(int,const T &)'
1> with
1> [
1> T=int
1> ]
1>c:devlinkedlistlinkedlistmain.cpp(50): note: see reference to function template instantiation 'void SingleLinkedList<int>::insertPosition(int,const T &)' being compiled
1> with
1> [
1> T=int
1> ]
1>c:devlinkedlistlinkedlistmain.cpp(23): note: see reference to class template instantiation 'SingleLinkedList<int>' being compiled
1>c:devlinkedlistlinkedlistsinglelinkedlist.h(186): error C2679: binary '=': no operator found which takes a right-hand operand of type 'SingleLinkedList<int>::Node *' (or there is no acceptable conversion)
1>c:program files (x86)microsoft visual studio2017communityvctoolsmsvc14.14.26428includememory(1390): note: could be 'std::shared_ptr<SingleLinkedList<int>::Node> &std::shared_ptr<SingleLinkedList<int>::Node>::operator =(std::shared_ptr<SingleLinkedList<int>::Node> &&) noexcept'
1>c:program files (x86)microsoft visual studio2017communityvctoolsmsvc14.14.26428includememory(1377): note: or 'std::shared_ptr<SingleLinkedList<int>::Node> &std::shared_ptr<SingleLinkedList<int>::Node>::operator =(const std::shared_ptr<SingleLinkedList<int>::Node> &) noexcept'
1>c:devlinkedlistlinkedlistsinglelinkedlist.h(186): note: while trying to match the argument list '(std::shared_ptr<SingleLinkedList<int>::Node>, SingleLinkedList<int>::Node *)'
1>c:devlinkedlistlinkedlistsinglelinkedlist.h(190): error C2664: 'std::shared_ptr<SingleLinkedList<int>::Node>::shared_ptr(std::shared_ptr<SingleLinkedList<int>::Node> &&) noexcept': cannot convert argument 1 from 'const int' to 'std::nullptr_t'
1>c:devlinkedlistlinkedlistsinglelinkedlist.h(190): note: only a null pointer constant can be converted to nullptr_t
1>c:devlinkedlistlinkedlistsinglelinkedlist.h(191): error C2679: binary '=': no operator found which takes a right-hand operand of type 'std::shared_ptr<SingleLinkedList<int>::Node>' (or there is no acceptable conversion)
1>c:program files (x86)microsoft visual studio2017communityvctoolsmsvc14.14.26428includememory(2309): note: could be 'std::unique_ptr<SingleLinkedList<int>::Node,std::default_delete<_Ty>> &std::unique_ptr<_Ty,std::default_delete<_Ty>>::operator =(const std::unique_ptr<_Ty,std::default_delete<_Ty>> &)'
1> with
1> [
1> _Ty=SingleLinkedList<int>::Node
1> ]
1>c:program files (x86)microsoft visual studio2017communityvctoolsmsvc14.14.26428includememory(2247): note: or 'std::unique_ptr<SingleLinkedList<int>::Node,std::default_delete<_Ty>> &std::unique_ptr<_Ty,std::default_delete<_Ty>>::operator =(std::unique_ptr<_Ty,std::default_delete<_Ty>> &&) noexcept'
1> with
1> [
1> _Ty=SingleLinkedList<int>::Node
1> ]
1>c:program files (x86)microsoft visual studio2017communityvctoolsmsvc14.14.26428includememory(2173): note: or 'std::unique_ptr<SingleLinkedList<int>::Node,std::default_delete<_Ty>> &std::unique_ptr<_Ty,std::default_delete<_Ty>>::operator =(std::nullptr_t) noexcept'
1> with
1> [
1> _Ty=SingleLinkedList<int>::Node
1> ]
1>c:devlinkedlistlinkedlistsinglelinkedlist.h(191): note: while trying to match the argument list '(std::unique_ptr<SingleLinkedList<int>::Node,std::default_delete<_Ty>>, std::shared_ptr<SingleLinkedList<int>::Node>)'
1> with
1> [
1> _Ty=SingleLinkedList<int>::Node
1> ]
1>Done building project "LinkedList.vcxproj" -- FAILED.
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
以下是我试图实现的功能：
template <class T>
void SingleLinkedList<T>::insertPosition(int pos, const T &theData) {
if (pos > getSize() || pos < 0) {
throw std::out_of_range("The insert location is invalid.");
}
else {
if (pos == 0) {
insertHead(theData);
}
else if (loc == getSize()) {
insertTail(theData);
}
else {
int nodeCount = 0;
std::shared_ptr<Node> ptr(head.get());
while (nodeCount < pos) {
ptr = ptr->next.get();
nodeCount++;
}
std::shared_ptr<Node> newNode(new Node(theData));
ptr->next = newNode;
}
}
}
这是整个头文件：
#ifndef SingleLinkedList_h
#define SingleLinkedList_h
#include <iostream>
template <class T>
class SingleLinkedList {
private:
struct Node {
T data;
std::unique_ptr<Node> next = nullptr;
Node(T x) : data(x), next(nullptr) {}
};
std::unique_ptr<Node> head = nullptr;
Node* tail = nullptr;
// This function is for the overloaded operator <<
void display(std::ostream &str) const {
for (Node* loop = head.get(); loop != nullptr; loop = loop->next.get()) {
str << loop->data << "t";
}
str << "n";
}
public:
// Constructors
SingleLinkedList() = default; // empty constructor
SingleLinkedList(SingleLinkedList const &source); // copy constructor
// Rule of 5
SingleLinkedList(SingleLinkedList &&move) noexcept; // move constructor
SingleLinkedList& operator=(SingleLinkedList &&move) noexcept; // move assignment operator
~SingleLinkedList();
// Overload operators
SingleLinkedList& operator=(SingleLinkedList const &rhs);
friend std::ostream& operator<<(std::ostream &str, SingleLinkedList &data) {
data.display(str);
return str;
}
// Memeber functions
void swap(SingleLinkedList &other) noexcept;
bool empty() const { return head.get() == nullptr; }
int getSize() const;
void push(const T &theData);
void push(T &&theData);
void display() const;
void insertHead(const T &theData);
void insertTail(const T &theData);
void insertPosition(int pos, const T &theData);
void deleteHead();
void deleteTail();
void deletePosition(int pos);
bool search(const T &x);
};
template <class T>
SingleLinkedList<T>::SingleLinkedList(SingleLinkedList<T> const &source) {
for(Node* loop = source->head.get(); loop != nullptr; loop = loop->next.get()) {
push(loop->data);
}
}
template <class T>
SingleLinkedList<T>::SingleLinkedList(SingleLinkedList<T>&& move) noexcept {
move.swap(*this);
}
template <class T>
SingleLinkedList<T>& SingleLinkedList<T>::operator=(SingleLinkedList<T> &&move) noexcept {
move.swap(*this);
return *this;
}
template <class T>
SingleLinkedList<T>::~SingleLinkedList() {
while (head != nullptr) {
deleteHead();
}
}
template <class T>
SingleLinkedList<T>& SingleLinkedList<T>::operator=(SingleLinkedList const &rhs) {
SingleLinkedList copy{ rhs };
swap(copy);
return *this;
}
template <class T>
void SingleLinkedList<T>::swap(SingleLinkedList &other) noexcept {
using std::swap;
swap(head, other.head);
swap(tail, other.tail);
}
template <class T>
int SingleLinkedList<T>::getSize() const {
int size = 0;
for (auto current = head.get(); current != nullptr; current = current->next.get()) {
size++;
}
return size;
}
template <class T>
void SingleLinkedList<T>::push(const T &theData) {
std::unique_ptr<Node> newNode = std::make_unique<Node>(theData);
if (head == nullptr) {
head = std::move(newNode);
tail = head.get();
}
else {
tail->next = std::move(newNode);
tail = tail->next.get();
}
}
template <class T>
void SingleLinkedList<T>::push(T &&thedata) {
std::unique_ptr<Node> newnode = std::make_unique<Node>(std::move(thedata));
if (head == nullptr) {
head = std::move(newnode);
tail = head.get();
}
else {
tail->next = std::move(newnode);
tail = tail->next.get();
}
}
template <class T>
void SingleLinkedList<T>::display() const {
Node* newNode = head.get();
while (newNode != nullptr) {
std::cout << newNode->data << "t";
newNode = newNode->next;
}
}
template <class T>
void SingleLinkedList<T>::insertHead(const T &theData) {
std::unique_ptr<Node> newNode = std::make_unique<Node>(theData);
newNode->next = std::move(head);
head = std::move(newNode);
}
template <class T>
void SingleLinkedList<T>::insertTail(const T &theData) {
std::unique_ptr<Node> newNode = std::make_unique<Node>(theData);
tail->next = std::move(newNode);
tail = tail->next.get();
}
template <class T>
void SingleLinkedList<T>::insertPosition(int pos, const T &theData) {
if (pos > getSize() || pos < 0) {
throw std::out_of_range("The insert location is invalid.");
}
else {
if (pos == 0) {
insertHead(theData);
}
else if (loc == getSize()) {
insertTail(theData);
}
else {
int nodeCount = 0;
std::shared_ptr<Node> ptr(head.get());
while (nodeCount < pos) {
ptr = ptr->next.get();
nodeCount++;
}
std::shared_ptr<Node> newNode(new Node(theData));
ptr->next = newNode;
}
}
}
template <class T>
void SingleLinkedList<T>::deleteHead() {
Node* old = head.get();
auto next = std::move(old->next);
head = std::move(next);
}
template <class T>
void SingleLinkedList<T>::deleteTail() {
}
template <class T>
void SingleLinkedList<T>::deletePosition(int pos) {
}
template <class T>
bool SingleLinkedList<T>::search(const T &x) {
}
#endif /* SingleLinkedList_h*/
以下是测试后一种功能的main.cpp文件：
#include <algorithm>
#include <cassert>
#include <iostream>
#include <ostream>
#include <iosfwd>
#include "SingleLinkedList.h"
int main(int argc, const char * argv[]) {
///////////////////////////////////////////////////////////////////////
///////////////////////////// Single Linked List //////////////////////
///////////////////////////////////////////////////////////////////////
SingleLinkedList<int> obj;
obj.push(2);
obj.push(4);
obj.push(6);
obj.push(8);
obj.push(10);
std::cout<<"n--------------------------------------------------n";
std::cout<<"---------------displaying all nodes---------------";
std::cout<<"n--------------------------------------------------n";
std::cout << obj << std::endl;
std::cout<<"n--------------------------------------------------n";
std::cout<<"-----------------Inserting At End-----------------";
std::cout<<"n--------------------------------------------------n";
obj.insertTail(20);
std::cout << obj << std::endl;
std::cout<<"n--------------------------------------------------n";
std::cout<<"----------------Inserting At Start----------------";
std::cout<<"n--------------------------------------------------n";
obj.insertHead(50);
std::cout << obj << std::endl;
std::cout<<"n--------------------------------------------------n";
std::cout<<"-------------inserting at particular--------------";
std::cout<<"n--------------------------------------------------n";
obj.insertPosition(5,60);
std::cout << obj << std::endl;
std::cout << "n--------------------------------------------------n";
std::cout << "-------------Get current size ---=--------------------";
std::cout << "n--------------------------------------------------n";
std::cout << obj.getSize() << std::endl;
// std::cout<<"n--------------------------------------------------n";
// std::cout<<"----------------Deleting At Start-----------------";
// std::cout<<"n--------------------------------------------------n";
// obj.deleteHead();
// std::cout << obj << std::endl;
//
// std::cout<<"n--------------------------------------------------n";
// std::cout<<"----------------Deleting At End-----------------";
// std::cout<<"n--------------------------------------------------n";
// obj.deleteTail();
// std::cout << obj << std::endl;
//
//
// std::cout<<"n--------------------------------------------------n";
// std::cout<<"--------------Deleting At Particular--------------";
// std::cout<<"n--------------------------------------------------n";
// obj.deletePosition(4);
// std::cout << obj << std::endl;
// std::cout << std::endl;
//
// obj.search(8) ? printf("Yes"):printf("No");
std::cin.get();
}
template <class T>
void SingleLinkedList<T>::insertPosition(int pos, const T &theData) {
if (pos > getSize() || pos < 0) {
throw std::out_of_range("The insert location is invalid.");
}
auto node = head.get();
int i = 0;
for (; node && node->next && i < pos; node = node->next.get(), i++);
if (i != pos) {
throw std::out_of_range("Parameter 'pos' is out of range.");
}
auto newNode = std::make_unique<Node>(theData);
if (node) {
newNode->next = std::move(node->next);
node->next = std::move(newNode);
}
else {
head = std::move(newNode);
}
}