double linked list delete function

Assignment_4.cpp

/*
Author: Mir Sahib
ID: 1510175
Assignment_4
*/
#include <iostream>

using namespace std;
struct node{
    int data;
    node* next;
    node* prev;
};
class List{
private:
    node* head;
    node* temp;
    node* curr;
public:
    List(){
        head = NULL;
        temp = NULL;
        curr = NULL;
    }
    void add(int element){
        temp = new node;
        temp->data = element;
        temp->next = NULL;
        temp->prev = NULL;
        if(head==NULL){
            head = temp;
        }else{
            curr = head;
            while(curr->next!=NULL){
                curr=curr->next;
            }
            curr->next = temp;
            temp->prev = curr;
        }
    }

    void display(){
        curr=head;
        while(curr!=NULL){
            if(curr->next==NULL){
                cout<<curr->data<<" ->NULL";
            }else{
                cout<<curr->data<<" -> ";
            }
            curr= curr->next;
        }
    }
    void reverseDisplay(){
        curr=head;
        while(curr->next!=NULL){
            curr=curr->next;
        }
        while(curr!=NULL){
            if(curr->prev==NULL){
                cout<<curr->data<<" ->NULL";
            }else{
                cout<<curr->data<<" -> ";
            }
            curr= curr->prev;
        }
    }
    //frequency
    int countOccurrent(int searchVal){
        int counter=0;
        if(head == NULL){
            cout<<"List is empty"<<endl;
        }else{
            curr = head;
            while(curr!=NULL){
                if(curr->data==searchVal){
                    counter++;
                }
                curr=curr->next;
            }
        }
        return counter;
    }

    //insert after first occurrence
    void insertAfter(int searchVal,int val){
        curr = head;
        if(head==NULL){
            cout<<"List is empty"<<endl;
        }else if(curr->data==searchVal){
            temp = new node;
            temp->data = val;
            temp->next = curr->next;
            curr->next = temp;
            temp->prev = curr;
        }else{
            int counter=0;
            while(curr!=NULL){
                if(curr->data==searchVal){
                    temp = new node;
                    temp->data = val;
                    temp->next = curr->next;
                    curr->next->prev = temp;
                    curr->next = temp;
                    temp->prev = curr;
                    counter++;
                    break;
                }
                curr=curr->next;
            }
            if(counter==0)cout<<"Search value not found"<<endl;
        }
    }
    //insert before first occurrence
    void insertBefore(int searchVal, int Val){
        curr = head;
        if(head==NULL){
            cout<<"List is empty"<<endl;
        }else if(curr->data == searchVal){
            temp = new node;
            temp->data = Val;
            temp->next = curr;
            curr->prev = temp;
            temp->prev = NULL;
            head = temp;
        }else{
            int counter=0;
            while(curr!=NULL){
                if(curr->data == searchVal){
                    temp = new node;
                    temp->data = Val;
                    temp->next = curr;
                    temp->prev = curr->prev;
                    curr->prev->next = temp;
                    curr->prev = temp;
                    counter++;
                    break;
                }
                curr=curr->next;
            }
            if(counter==0)cout<<"\nSearch value not found";
        }
    }
    void deleteFirstOccurrence(int searchVal){
        curr=head;
        if(head==NULL){
            cout<<"List is empty"<<endl;
        }else if(curr->data == searchVal){
            curr->next->prev=NULL;
            head = curr->next;
            delete curr;
        }else{
            int counter=0;
            while(curr!=NULL){
                if(curr->data == searchVal){
                    curr->prev->next = curr->next;
                    if(curr->next!=NULL){//if not last node
                        curr->next->prev = curr->prev;
                    }
                    delete curr;
                    counter++;
                    break;
                }
                curr=curr->next;
            }
            if(counter==0)cout<<"\nSearch value not found"<<endl;
        }
    }
    void deleteLastOccurrence(int searchVal){
        curr=head;
        if(head==NULL){
            cout<<"List is empty"<<endl;
        }else{
            int counter=0;
            while(curr!=NULL){
                if(curr->data==searchVal){
                    temp = curr;
                    counter++;
                }
                curr=curr->next;
            }
            if(counter!=0){
                temp->prev->next=temp->next;
                if(temp->next!=NULL){//if not last node
                    temp->next->prev = temp->prev;
                }
                delete temp;
            }else{
                cout<<"\nSearch value not found";
            }
        }
    }

};

int main()
{
    List myList;
    for(int i=0;i<5;i++){
        myList.add(i+1);
    }
   // myList.insertBefore(3,43);
    //myList.insertAfter(2,21);
    cout<<"Initial List"<<endl;
    myList.display();
    cout<<endl;
    myList.reverseDisplay();
    cout<<"\nDelete first occurrence";
    myList.deleteFirstOccurrence(1);
    cout<<endl;
    myList.display();
    cout<<endl;
    myList.reverseDisplay();
    cout<<"\nDelete Last occurrence";
    myList.deleteLastOccurrence(1);
    cout<<endl;
    myList.display();
    cout<<endl;
    myList.reverseDisplay();

    return 0;
}