linklist operations without remove

/* error in remove */

#include<cstdio>
#include<iostream>
using namespace std;

void push(int x);
void pop();
void search(int x);
void update(int oldvalue,int newvalue);
void remove(int num);
//void insert(int afterwhich,int numbertoinsert);

typedef struct alvi
{
    int data;
    struct alvi *prev;
    struct alvi *next;
}node;

node *head = NULL;
node *tail = NULL;

int main(void)
{
    int choice,push_number,search_number,remove_number,olds,news;
    while(1)
    {
        printf("Choose : 1 to push,2 to pop,3 to search,4 to update,5 to remove,6 to quit\n");
        scanf("%d",&choice);
        switch(choice)
        {
            case 1:
                printf("Enter number to push : ");
                scanf("%d",&push_number);
                push(push_number);
                break;
            case 2:
                pop();
                break;
            case 3:
                printf("Enter number to search : ");
                scanf("%d",&search_number);
                search(search_number);
                break;
            case 4:
                printf("Enter a old value :");
                scanf("%d",&olds);
                printf("Enter a new value :");
                scanf("%d",&news);
                update(olds,news);
                break;
            case 5:
                printf("Enter a number to remove : ");
                scanf("%d",&remove_number);
                remove(remove_number);
                break;
            case 6:
                return 0;
            default:
                printf("Wrong input \n");
                break;

        }
    }
    return 0;
}
void push(int x)
{
    node *newNode = new node();
    newNode->data = x;
    if(head==NULL)
    {
        cout<<"First node pushed"<<endl;
        newNode->prev=NULL;
        newNode->next=NULL;
        head=newNode;
        tail=newNode;
    }
    else
    {
        cout<<"other node pushed"<<endl;
        head->prev=newNode;
        newNode->next=head;
        head=newNode;
    }
}
void pop()
{
    node *cursor;
    cursor = tail;
    while(cursor!=NULL)
    {
        cout<<cursor->data<<" ";
        cursor=cursor->prev;
    }
    cout<<endl;
}
void search(int x)
{
    node *cursor1;
    cursor1 = head;
    int flag=0;
    int counter = 1;
    while(cursor1!=NULL)
    {
        if(cursor1->data==x)
        {
            flag=1;
            cout<<"found"<<endl;;
            cout<<"element number : "<<counter<<endl;
            break;
        }
        cursor1=cursor1->next;
        counter++;
    }
    if(flag==0)
    {
        cout<<"not found"<<endl;
    }
}
void update(int oldvalue,int newvalue)
{
    node *cursor2;
    cursor2 = head;
    int flag=0;
    //int counter = 1;
    while(cursor2!=NULL)
    {
        if(cursor2->data==oldvalue)
        {
            flag=1;
            cursor2->data=newvalue;
            break;
        }
        cursor2=cursor2->next;
        //counter++;
    }
    if(flag==0)
    {
        cout<<"not found"<<endl;
    }
}
void remove(int num)
{
    node *cursor3;
    cursor3 = head;
    int flag=0;
    //int counter = 1;
    while(cursor3!=NULL)
    {
        if(cursor3->data==num && (cursor3->next==NULL || cursor3->prev==NULL ))
        {
            flag=2;
            if( (cursor3->prev!=NULL && cursor3->next==NULL ) )
            {
                flag=3;
                cursor3->prev=NULL;
                break;
            }
            if( (cursor3->prev==NULL && cursor3->next!=NULL ) )
            {
                flag=4;
                cursor3->next=NULL;
                break;
            }
            if( (cursor3->prev==NULL && cursor3->next==NULL ) )
            {
                flag=5;
            }




            if(flag==3)
            {

            }
            if(flag==4)
            {

            }
            if(flag==5)
            {

            }


        }
        if(cursor3->data==num && cursor3->next!=NULL && cursor3->prev!=NULL   )
        {
            flag=1;
            (cursor3->prev)->next = cursor3->next;
            (cursor3->next)->prev = cursor3->prev;
            break;
        }
        cursor3=cursor3->next;
        //counter++;
    }
    cout<<flag;
    if(flag==0)
    {
        cout<<"not found"<<endl;

    }
}
/*
void insert(int afterwhich,int numbertoinsert)
{
    node *cursor4;
    cursor4 = head;
    int flag=0;
    //int counter = 1;
    while(cursor4!=NULL)
    {
        if(cursor4->data==afterwhich)
        {
            flag=1;

            break;
        }
        cursor4=cursor4->next;
        //counter++;
    }
    if(flag==0)
    {
        cout<<"not found"<<endl;
    }
}
*/