C + + implements doubly linked list

Doubly linked list

#include <iostream>using namespace std;typedef int datatype;struct node{node ( CONST&NBSP;DATATYPE&AMP;D): _data (d),  _next (null),  _prev (null) {}node*_next; node*_prev;datatype _data;}; class dlist{friend ostream&operator<< (ostream&os, dlist& d);p ublic:dlist (): _head (null),  _tail (null) {}~dlist () {node*cur=_head;while  (cur) {node*del = cur;cur =  cur->_next;delete del;}} Public:void pushback (const datatype&d);//tail plug void popback ();//tail-delete Void pushfront (const &NBSP;DATATYPE&AMP;D);//Head inserted Void popfront ();//head-cut 2private:node*_head; Node*_tail;};o stream&operator<< (ostream&os, dlist& d) {Node* cur = d._head;while   (cur) {cout << cur->_data <<  "<=>"; cur = cur->_next ;} cout <<  "Over" &NBSP;&LT;&LT;&NBSP;ENDL;RETURN&NBSP;OS;} Void dlist::P ushback (const D atatype&d)//tail plug {node*newnode = new node (d);if  (_head == null) {_head =  newnode;_tail = newnode;} Else{_tail->_next = newnode;newnode->_prev = _tail;_tail = newnode;}} Void dlist::P opback ()//tail Delete {if  (_head == null)//No node {return;} if  (_head == _tail)//a node {delete _tail;_head = null;_tail = null; return;} Multi-node _tail = _tail->_prev;delete _tail->_next;_tail->_next = null;} Void dlist::P ushfront (const datatype&d)//head Insert {node*newnode = new node (d);if  (_ Head == null) {_head = newnode;_tail = newnode;} Else{newnode->_next = _head;_head->_prev = newnode;_head = newnode;}} Void dlist::P Opfront ()//First delete {if  (_head == null) {return;} if  (_head == _tail) {delete _tail;_tail = null;_head = null;return;} Node*del = _head;_head = _head->_next;_head->_prev = null;delete del;} Node*dlist::find (CONST&NBSP;DATATYPE&AMP;D)//Find {node*cur = _head;while  (cur) {if  (cur->_ DATA&NBSP;==&NBSP;D) {return cur;} Cur = cur->_next;} Return null;} Void dlist:: insert (NODE*&NBSP;POS,&NBSP;CONST&NBSP;DATATYPE&AMP;D)//Insert {Node*newNode = new  node (d);if  (pos == _tail) {_tail->_next = newnode;newnode->_prev =  _tail;_tail = newnode;} Else{newnode->_next = pos->_next;pos->_next->_prev = newnode;newnode->_prev  = pos;pos->_next = newnode;}}

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C + + implements doubly linked list