数据结构:链表

//
// Created by DevilInChina on 2018/6/25.
//

#include <iostream>
#include <algorithm>
#include <functional>
using namespace std;
template <typename T>
class List;
template <typename T>
class node{///双向链表节点，存储前指针后指针及元素本身。
    friend class List<T>;
    node *pre;
    node *next;
public:
    T ele;
    node(T &A):ele(A){
        pre = nullptr;
        next= nullptr;
    }
    node(){
        pre = nullptr;
        next= nullptr;
    }
    T&operator*(){ return ele;}
    ~node(){
    }
};
template <typename T>
class List{
private:///pData为链表表头,en为链表表尾均不存放数据
    unsigned cnt;///元素个数计数
    node <T>*pData;
    node <T>*en;
    node <T>*last;///最后一个实际元素节点
public:
    ///与iterator类混合使用，进行迭代访问。
    node<T> *begin(){ return pData->next;}
    node<T> *end(){ return en;}
    class iterator{
        node<T>*p;
        friend class List<T>;
    public:
        T&operator*(){
            return p->ele;
        }
        node<T>*operator++(){
            ///没有设计超限访问报错,因为笔者认为是用户的错
            p = p->next;
            return p;
        }
        bool operator!=(node<T>*t){ return p!=t;}
        bool operator==(node<T>*t){ return p==t;}
        void operator=(node<T>*t){p = t;}
    };
    ///构造之初均设计好首尾节点
    List(){
        cnt = 0;
        pData = new node<T>;
        en = new node<T>;
        last = pData;
        en->pre = pData;
        pData->next = en;
    }
    List(T*a,T*b){
        cnt = (unsigned int)(b - a);
        pData = new node<T>;
        last = pData;
        while (a!=b){
            last->next = new node<T>(*a);
            last ->next ->pre = last;
            last = last->next;
            a++;
        }
        en = new node<T>;
        en->pre = last;
        last->next = en;
    }
    List(T a, unsigned int n){
        cnt = 0;
        pData = new node<T>;
        last = pData;
        while (cnt!=n){
            last->next = new node<T>(a);
            last ->next ->pre = last;
            last = last->next;
            ++cnt;
        }
        en = new node<T>;
        en->pre = last;
        last->next = en;
    }
    ///可更改排序规则的排序，实现一劳永逸，默认情况需要元素重载小于号运算符
    void sort(std::function<bool(const T&,const T&)> cmp
    = [&](const T&a,const T&b)->bool{ return a < b;}){
        node<T>**dat;
        node<T>*it;
        dat = new node<T>* [cnt];
        it = pData->next;
        std::function<bool(const node<T>*,const node<T>*)> fun;
        fun = [&](const node<T>*a,const node<T>*b)->bool{
            return cmp(a->ele,b->ele);
        };
        for(int i = 0 ; i < cnt ; ++i){
            dat[i]=it;///为新生成的指针数组初始化
            it=it->next;
        }
        std::sort(dat,dat+cnt,fun);
        ///进行索引排序，避免大量复制
        for(int i = 0 ; i < cnt ; ++i){
            if(i!=cnt-1)dat[i]->next=dat[i+1];
            if(i)dat[i]->pre = dat[i-1];
        }
        pData->next=dat[0];
        dat[0]->pre=pData;
        dat[cnt-1]->next = en;
        en->pre = dat[cnt-1];
        last = dat[cnt-1];
        delete []dat;
    }
    T&front(){
        return pData->next->ele;
    }
    void push_back(T A){
        last -> next = new node<T>(A);
        last ->next ->pre = last;
        last = last->next;
        last->next = en;;
        en->pre = last;
        cnt++;
    }
    void push_front(T A){
        if(pData->next== nullptr){
            push_back(A);
            return;
        }
        node<T>*p = new node<T>(A);
        p->next = pData->next;
        pData->next->pre = p;
        pData->next = p;
        p->pre = pData;
        cnt++;
    }
    void pop_back(){
        last = last->pre;
        delete last->next;
        last->next = en;
        en->pre = last;
        --cnt;
    }
    void pop_front(){
        node<T>*tmp = pData->next;
        pData->next = tmp->next;
        tmp->next->pre = pData;
        delete tmp;
        --cnt;
    }
    ///三个insert实际上都依靠最后的insert完成，减少代码量，略微增加机器的负担
    ///且超出长度默认合并到最后一项，没有提示
    void insert(unsigned int pos,T*A,T*B){
        List <T> C(A,B);
        insert(pos,C);
    }
    void insert(unsigned int pos,T A){
        T pa[2];
        pa[0] = A;
        insert(pos,pa,pa+1);
    }
    void insert(unsigned int pos,List<T>&A){
        if(pos>=cnt){
            merge(A);
        }
        else {
            node<T> *it = pData;
            while (pos--) {
                it = it->next;
            }
            A.last->next = it->next;
            it->next->pre=A.last;
            it->next = A.pData->next;
            A.pData->next->pre = it;
            A.pData->next = A.en;
            A.en->pre = A.pData;
            cnt+=A.cnt;
            A.cnt = 0;
        }
    }
    node<T>* erase(iterator i){///删除元素后返回上一个元素指针
        if(i.p== en)
            return en->pre;
        node<T>*tmp = i.p;
        i.p = i.p->pre;
        tmp->pre->next = tmp->next;
        tmp->next->pre = tmp->pre;
        delete tmp;
        return i.p;
    }
    node<T>*find(T a) {///只用定义了 < 运算符的元素可以进行查找
        node<T>*ipos = pData;
        while (ipos->next!=en){
            if(!(ipos->ele<a)&&!(a<ipos->ele))
                return ipos;
            ipos = ipos->next;
        }
        return en;
    }
    void merge(List<T>&A){
        if(!A.size())///没有这一句会出问题导致链表自环
            return;
        last->next = A.pData->next;
        A.pData->next->pre = last;
        A.last->next = en;
        en->pre = A.last;
        last = A.last;
        A.last = A.pData;
        A.pData->next = A.en;
        A.en->pre = A.pData;
        cnt+=A.cnt;
        A.cnt = 0;
    }
    void clear(){
        while (pData->next!=en){
            pData = pData->next;
            delete pData->pre;
        }
        pData->next = en;
        en->pre = pData;
        cnt = 0;
    }
    T&operator[](unsigned int k){
        if(k>=cnt){
            cerr<<"seg fault"<<"
";
            return pData->ele;
        }
        node<T>* it = pData;
        while (k--){
            it = it->next;
        }
        return it->next->ele;
    }
    unsigned int size(){ return cnt;}
    unsigned int length(){ return cnt;}
    ~List(){
        while (pData->next){
            pData = pData->next;
            delete pData->pre;
        }
        delete pData;
        delete en;
    }
};
int main(){
    /// test
}