Signal Encoding Scheme Simulations in C++

Question

I am doing a project for my communication networks class in C++. Basically I am given a set of digits "1010011010" and I have to convert it into a bandwidth NRZ-L, NRZ-I, B-AMI, Manchester and D-Manchester.

I was able to do the first two bandwidths and I am currently doing the B-AMI. So what I created was a doubly linked list that holds the digits and a pointer "current" that points to each node. Then I created an array that will store a string depending on the data that the pointer is pointing to. This is what it looks like on paper.

There is a "c" for my current pointer, a "t" for my temp pointer, an "i" for my index in the array and a "j" so that it can move backwards.

As you can see, I commented out my else if statement under my BAMI function. If I were to uncomment it, and try to run it, the program will crash. My BAMI function is supposed to output "-V 0 +V 0 0 -V +V 0 -V 0".

If anyone can help me out I would gladly appreciate it.

Thanks!

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

template <class OPERATOR>
class doublyLinkedList{
private:
    class node{
    public:
        OPERATOR data;
        node * next;
        node * prev;
    };

    node * head; //ptr to first node in list
    node * tail; //ptr to last node in list


public:
    void insert_at_back(OPERATOR x){
        node * ptr = new node;
        ptr->data = x;
        if (tail == NULL){ //empty list
            head = ptr;
            ptr->prev = NULL;
            tail = ptr;
            ptr->next = NULL;
        }else{ //list not empty
            tail->next = ptr;
            ptr->prev = tail;
            ptr->next = NULL;
            tail = ptr;
        }
    }

    void printList(){
        node * zombie = head;
        while (zombie != NULL){
            cout << zombie->data;
            zombie = zombie->next;
        }
    }

    //NRZ-L Formula
    void NRZL(){
        node * current = head;
        while (current->next != NULL){
            if (current->data == 1){
                cout << "|-V ";
                current = current->next;
            }else if (current->data == 0){
                cout << "|+V ";
                current = current->next;
            }
        }

        if (tail->data == 0){
            cout << "|+V |" << endl;
        }else{
            cout << "|-V |" << endl;
        }
    }

    //NRZ-I Formula
    void NRZI(){
        node * current = head;
        string value[10];
        while (current != NULL){
            for (int i = 0; i < 10; i++){
                if ( (current->data == 1 || current->data == 0)
                     && current->prev == NULL){
                    //If first bit in node is 1 or 0, it will be -V
                    value[i] = "|-V ";
                }else if (current->data == 0 && current->prev->data == 1){
                    //Checking if previous is 1 and current is 0
                    value[i] = value[i - 1];
                }else if (current->data == 0 && current->prev->data == 0){
                    //Checking if previous and current is 0
                    value[i] = value[i - 1];
                }else if (current->data == 1 && current->prev->data == 1){
                    //Checking is previous and current is 1
                    if (value[i - 1] == "|-V "){
                        //Checking is previous index is -V
                        value[i] = "|+V ";
                    }else{ //Checking is previous index is +V
                        value[i] = "|-V ";
                    }
                }else if (current->data == 1
                          && current->prev->data == 0){
                    //Checking is previous is 0 and current is 1
                    if (value[i - 1] == "|-V "){
                        //Checking if previous index is -V
                        value[i] = "|+V ";
                    }else{ //Checking if previous index is +V
                        value[i] = "|-V ";
                    }
                }
                current = current->next;
            }
        }
        for (int i = 0; i < 10; i++)//Printing the array
            cout << value[i];
        cout << "|" << endl;
    }


    //B-AMI formula
    void BAMI(){////Fix this code. Keeps crashing
        node * current = head;
        string value[10];
        while (current != NULL){
            for (int i = 0; i < 10; i++){
                if ((current->data == 1 || current->data == 0)
                    && current->prev == NULL){
                    //If current is first bit it will be -V
                    value[i] = "|-V ";
                }

                //else if (current->data == 1 && current->prev->data != 1){
                //    //If current is 1 and prev is 0
                //    node * temp = current->prev;//
                //    for (int j = i-1; j < i; j--){
                //      if (temp->prev->data != 1){
                //          temp = temp->prev;                      
                //      }else{
                //          if (value[j-1] == "|-V "){
                //              value[i] = "|+V ";
                //          }else if (value[j-1] == "|+V "){
                //              value[i] = "|-V ";
                //          }
                //      }
                //  }
                //  delete temp;
                //}

                else{//If current is 0
                    value[i] = "|0 ";
                }

                current = current->next;

            }
        }
        for (int i = 0; i < 10; i++)//Printing the array
            cout << value[i];
        cout << "|" << endl;
    }



    //Manchester formula

    //D-Manchester formula


    //constructor
    doublyLinkedList(){
        head = NULL;
        tail = NULL;
    }
};



int main(){

    doublyLinkedList<int> numberList; 
    cout << "This is the original binary code:";

    numberList.insert_at_back(1);
    numberList.insert_at_back(0);
    numberList.insert_at_back(1);
    numberList.insert_at_back(0);
    numberList.insert_at_back(0);
    numberList.insert_at_back(1);
    numberList.insert_at_back(1);
    numberList.insert_at_back(0);
    numberList.insert_at_back(1);
    numberList.insert_at_back(0);
    cout << endl;
    numberList.printList();
    cout << endl;
    cout << "=========================================" << endl << endl;

    cout << "This is NRZ-L:" << endl;
    numberList.NRZL();
    cout << "=========================================" << endl << endl;

    cout << "This is NRZ-I:" << endl;
    numberList.NRZI();
    cout << "=========================================" << endl << endl;

    cout << "This is B-AMI:" << endl;
    numberList.BAMI();///fix function for this code to work
    cout << "=========================================" << endl << endl;

    system("pause");
    return 0;
}