数据结构<一>单链表

#include<iostream>
#include<cstdlib>
#include<cstring>
using namespace std;
struct Node{
  int date;
  Node* next;
};
class List{
  private:
    Node *head;
  public:
    List() {
      head = new Node;
      head->date = 0;
      head->next = NULL; 
    }
    ~List() {
      delete head;
    }
    int Length();
    bool IsEmpty(); 
    void Insert(int x,int k); 
    void Delete(int k); 
    void ClearList(); 
    void Output();    
};
int List::Length() {
  Node *q = head->next;
  int k = 0;
  while (q) {
    k++;
    q = q->next;
  }
  return k;
}
bool List::IsEmpty(){
  return head->next == NULL;
}
void List::Insert(int x, int s) {
  if (x < 1) {
    cout<<"NO"<<endl;
    exit(1);
  }
  int k = 0;
  Node *q = head;
  while (q&& k < x-1) {
    k++;
    q = q->next;
  }
  if (!q) {
    cout<<"NO"<<endl;
    exit(1);
  }
  Node *p = new Node;
  p->date = s;
  p->next = q->next;
  q->next = p;
}
void List::Delete(int x) {
  if (x < 1) {
    cout<<"NO"<<endl;
    exit(1);
  }
  int k = 0;
  Node *q = head;
  while (q&& k < x-1) {
    k++;
    q = q->next;
  }
  if (q->next == NULL) {
    cout<<"NO"<<endl;
    exit(1);
  }
  Node *p = q->next;
  q->next = p->next; 
} 
void List::ClearList() {
  Node *q = head->next;
  while (q) {
    Node *p = q;
    q = q->next;
    delete p;
  }
  head->next = NULL;
}
void List::Output() {
  Node *q = head->next;
  while (q) {
    cout<<q->date<<" ";
    q = q->next;
  }
  cout<<endl;
}
int main() {
  List l;
  l.Insert(1,2);
  l.Insert(2,3);
  l.Insert(3,4);
  l.Insert(4,5);
  l.Output();
  l.Delete(2);
  l.Output();
  cout<<l.Length();
  return 0;
}