123

#include "stdafx.h"
#include <iostream>
#include <conio.h>

using namespace std;

struct Node{
    int d;
    Node *next;
    Node *prev;
};

Node * first (int d);
void add (Node ** pend, int d);
Node *find (Node *const pbeg, int i);
bool remove (Node **pbeg, Node **pend, int key);
Node * insert (Node * const pbeg, Node **pend, int key, int d);

int main() {
    Node *pbeg = first(1);
    Node *pend = pbeg;
    for (int i=2; i<6;i++) add (&pend, i);
    insert (pbeg, &pend,2,200);
    if (!remove (&pbeg, &pend, 5)) cout << "не найден";
    Node *pv  = pbeg;
    while (pv) {
        cout << pv ->d << ' ';
        pv = pv->next;
    }
    system ("Pause");
    return 0;
}

Node *first (int d) {
    Node *pv = new Node;
    pv->d = d; pv-> next = 0; pv-> prev = 0;
    return pv;
}

void add (Node **pend, int d)
{
    Node *pv = new Node;
    pv->d=d; pv->next=0; pv->prev=*pend;
    (*pend)->next=pv;
    *pend=pv;
}

Node *find(Node *const pbeg, int d) {
    Node *pv = pbeg;
    while (pv) {
        if (pv->d == d) break;
        pv=pv->next;
    }
    return pv;
}

bool remove (Node **pbeg, Node **pend, int key) {
    if (Node *pkey = find (*pbeg, key)) {
        if (pkey == *pbeg) {
            *pbeg = (*pbeg) -> next;
            (*pbeg)->prev=0;
        } else if (pkey == *pend) {
            *pend = (*pend) -> prev;
            (*pend)->next=0;
        } else {
            (pkey -> prev) -> next = pkey -> next;
            (pkey -> next) -> prev = pkey -> prev;
        }
        delete pkey;
        return true;
    }
    return false;
}

Node * insert (Node * const pbeg, Node **pend, int key, int d) {
    if (Node *pkey = find (pbeg, key)) {
        Node *pv=new Node;
        pv->d = d;
        pv->next=pkey->next;
        pv->prev=pkey;
        pkey->next=pv;
        if(pkey != *pend) (pv->next)->prev=pv;
        else *pend = pv;
        return pv;
    }
    return 0;
}