C++实现简单单向链表

#pragma once
#include
using namespace std;
struct Node//节点
{
 int value;
 Node* next;
 Node(int a = 0, Node* n = NULL) :value(a), next(n) {}
};
class List
{
private:
 Node* head = NULL;//头指针
 Node* tail = NULL;//尾指针，便于在尾部添加节点
 int size = 0;
public:
 int getSize() { return size; }//获取链表大小
 void print();//打印链表
 void append(int a);//右添加
 void appendleft(int a);//左添加
 void remove(int a);//删除节点
};

void List::append(int a)
{
 Node *p = new Node(a);
 if (head)
 {
 tail->next = p;
 tail = p;
 }
 else
 {
 head = p;
 tail = p;
 }
 size++;
}
void List::appendleft(int a)
{
 Node *p = new Node(a);
 if (head)
 {
 p->next = head;
 head = p;
 }
 else
 {
 head = p;
 tail = p;
 }
 size++;
}
void List::remove(int a)
{
 Node* p = head;
 bool flag = false;
 if (!head)
 {
 flag = false;
 cout <<"链表已空，无需删除！" <value == a && head != tail)
 {
 head = head->next;
 delete p;
 size--;
 flag = true;
 cout <<"删除成功！" <value == a && head == tail)
 {
 head = NULL, tail = NULL;
 delete p;
 size--;
 flag = true;
 cout <<"删除成功！" <next;
 while (q)
 {
  if (q->value == a && q != tail)
  {
  p->next = q->next;
  delete q;
  size--;
  flag = true;
  cout <<"删除成功！" <value == a && q == tail)
  {
  p->next = NULL;
  tail = p;
  delete q;
  size--;
  flag = true;
  cout <<"删除成功！" <next;
  }
 }
 if (!flag)
  cout <<"查无此值:" <value <<" ";
  p = p->next;
 }
 cout <