1 #include<iostream>
  2 using namespace std;
  3
  4 class Node {
  5 public:
  6     int data;
  7     Node *next;
  8     Node(int da):
  9         data(da), next(NULL){}
 10 };
 11
 12 class List{
 13 public:
 14     Node *head;
 15     List(): head(NULL){}
 16     ~List(){
 17         delete head;
 18         cout<<"The list is deleted."<<endl;
 19     };
 20     int size(); // 链表长度
 21     void printList(); // 打印链表
 22     void insert(int position, int value); // 指定位置插入
 23     void insertHead(int value); // 插入到最前
 24     void insertTail(int value); // 插入到最后
 25     void reverse();
 26 };
 27
 28 // 返回链表大小
 29 int List::size(){
 30     Node *p = head;
 31     int index = 0;
 32     while(p != NULL){
 33         index++;
 34         p = p->next;
 35     }
 36     return index;
 37 }
 38
 39 // 打印链表
 40 void List::printList(){
 41     Node *p = head;
 42     while(p != NULL){
 43         cout<<p->data<<" ";
 44         p = p->next;
 45     }
 46     cout<<endl;
 47
 48     p = head;
 49     while(p != NULL){
 50         cout<<p<<" ";
 51         p = p->next;
 52     }
 53     cout<<endl<<endl;
 54 }
 55
 56 // 在position位置插入value
 57 void List::insert(int position, int value){
 58     if(position<0 || position>List::size()){
 59         cout<<"position error, please check."<<endl;
 60         return ;
 61     }
 62     Node *s = new Node(value); // new node
 63     Node *p = head;
 64     if(head == NULL){ // isEmpty = true
 65         head = s;
 66     }
 67     else{ // isEmpty = false
 68         if(position == 0){
 69             s->next = p;
 70             head = s;
 71         }
 72         else{
 73             int index = 0;
 74             while(index != position-1){
 75                 p = p->next;
 76                 index++;
 77             }
 78             s->next = p->next;
 79             p->next = s;
 80         }
 81     }
 82     if (position == 0)
 83         cout<<"insert "<<value<<" at the first."<<endl;
 84     else if (position == List::size())
 85         cout<<"insert "<<value<<" at the tail."<<endl;
 86     else
 87         cout<<"insert "<<value<<" at position "<<position<<endl;
 88 }
 89
 90 // 头部插入
 91 void List::insertHead(int value){
 92     List::insert(0, value);
 93 }
 94
 95 // 尾部插入
 96 void List::insertTail(int value){
 97     List::insert(List::size(), value);
 98 }
 99
100 // 反转链表
101 void List::reverse(){
102     if (head == NULL || head->next == NULL)
103         return ;
104     Node *prev = head;
105     Node *cur = head->next;
106     Node *temp = head->next->next;
107     while(cur){
108         temp = cur->next;
109         cur->next = prev;
110         prev = cur;
111         cur = temp;
112     }
113     head->next = NULL; // 更新末尾元素的指针
114     head = prev; // 更新头结点
115 }
116
117 int main() {
118     List l1;
119     l1.insertTail(6);
120     l1.insertHead(7);
121     l1.insert(1, 5);
122     l1.insert(0, 16);
123     l1.insert(2, 56);
124     l1.insert(0, 169);
125     l1.insert(6, 16);
126     cout<<endl<<"The list is:"<<endl;
127     l1.printList();
128     l1.reverse();
129     cout<<endl<<"The reversed list is:"<<endl;
130     l1.printList();
131     return 0;
132 }