链表经典算法

#include <iostream>
using namespace std;
typedef int T;
class List{
    struct Node{
        T         data;
        Node*     next;
        Node(const T& d=T()):data(d),next(0){}//零初始化
    };
    Node* head;//头指针，用来保存头节点的地址
    int len;
public:
    List():head(NULL),len(0){ }
    void push_front(const T& d){
   //前插
        insert(d,0);
    }
    List& push_back(const T& d){
   //尾插
        insert(d,size());
        return *this;
    }
    int size()const{
        return len;
    }
    Node*& getptr(int pos){
   //找链表中指向指定位置的指针
        if(pos<0||pos>size()) pos=0;
        if(pos==0) return head;
        Node* p = head;
        for(int i=1; i<pos; i++)
            p = p->next;
        return (*p).next;
    }
    void insert(const T& d, int pos){
   //在任意位置插入
        Node*& pn = getptr(pos);
        Node* p = new Node(d);
        p->next = pn;
        pn = p;
        ++len;
    }
    void travel()const{
   //遍历
        Node* p = head;
        while(p!=NULL){
            cout << p->data << ' ';
            p = p->next;
        }
        cout << endl;
    }
    void clear(){
   //清空这个链表
        while(head!=NULL){
            Node* p = head->next;
//            cout << "delete " << head << endl;
            delete head;
            head = p;
        }
        len = 0;
    }
    ~List(){
//        cout << this << "*******" << head << endl;
        clear();
    }
    void erase(int pos){
   //有效位置为0～size()-1
        if(pos<0||pos>=size()) return;
        Node*& pn = getptr(pos);
        Node* p = pn;
        pn = pn->next;
        delete p;
        --len;
    }
    void remove(const T& d){
        int pos;
        while((pos=find(d))!=-1)
            erase(pos);
    }
    int find(const T& d)const{
        int pos = 0;
        Node* p = head;
        while(p){
            if(p->data==d) return pos;
            p = p->next; ++pos;
        }
        return -1;
    }
    void set(int pos, const T& d){
        if(pos<0||pos>=size()) return;
        getptr(pos)->data = d;
    }
    bool empty()const{
   return head==NULL;}
    T front()const{
   if(empty())throw "空";return head->data;}
    T back()const{
        if(empty())throw "空";
        Node* p=head;
        while(p->next!=NULL)
            p = p->next;
        return p->data;
    }
};
int main()
{
    List l;
    l.push_front(5);//5
    l.push_front(8);//8 5
    l.push_front(20);//20 8 5
    l.insert(9,2);//20 8 9 5
    l.insert(6,100);//6 20 8 9 5
    l.insert(7,-10);//7 6 20 8 9 5
    l.insert(1,2);//7 6 1 20 8 9 5
    l.push_back(10).push_back(15).travel();
    l.erase(0);//x7:6 1 20 8 9 5 10 15
    l.erase(l.size()-1);//x15:6 1 20 8 9 5 10
    l.erase(2);//x20:6 1 8 9 5 10
    l.travel();
    l.push_back(6);//6 1 8 9 5 10 6
    l.insert(6, 3);//6 1 8 6 9 5 10 6
    l.travel();
    l.remove(6);//1 8 9 5 10
    l.travel();
    l.set(0, 666);
    l.set(4, 789);
    l.set(l.find(9),123);
    l.set(1, 777);
    l.travel();
    cout << l.front() << "..." << l.back() << ',' << l.size() << "个" << endl;
    while(!l.empty()) l.erase(0);
    cout << "size:" << l.size() << endl;
    return 0;
}