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  1. If there is no middle node in the list to delete, return an empty list (i.e. NULL).    
  2. If there are two middle nodes in the list, delete the first one.

 using namespace std;

    //Following is the linked list node structure:
    template <typename T>
    class Node {
        T data;
        Node* next;

        Node(T data) {
            next = NULL;
            this->data = data;

        ~Node() {
            if (next != NULL) {
                delete next;

Node<int>* deleteMiddle(Node<int>* head){
    // Write your code here.
    if(head == NULL){
        return NULL;
    if(head->next == NULL){
        delete head;
        return NULL;
    Node<int>* ft = head;
    Node<int>* st = head;
    Node<int>* prev;
    while(ft->next != NULL && ft->next->next != NULL){
        prev = st;
        ft = ft->next->next;
        st = st->next;
    prev->next = st->next;
    delete st;
    return head;

What I have tried:

I tried to run this code. But it is showing Runtime error.
//I did not declare main() function above as it is already there where I have tried to solve it.
Updated 5-Jun-21 3:37am
Richard MacCutchan 5-Jun-21 3:38am    
"But it is showing Runtime error."
Do you not think it would be a good idea to explain what error you see?

Compiling does not mean your code is right! :laugh:
Think of the development process as writing an email: compiling successfully means that you wrote the email in the right language - English, rather than German for example - not that the email contained the message you wanted to send.

So now you enter the second stage of development (in reality it's the fourth or fifth, but you'll come to the earlier stages later): Testing and Debugging.

Start by looking at what it does do, and how that differs from what you wanted. This is important, because it give you information as to why it's doing it. For example, if a program is intended to let the user enter a number and it doubles it and prints the answer, then if the input / output was like this:
Input   Expected output    Actual output
  1            2                 1
  2            4                 4
  3            6                 9
  4            8                16
Then it's fairly obvious that the problem is with the bit which doubles it - it's not adding itself to itself, or multiplying it by 2, it's multiplying it by itself and returning the square of the input.
So with that, you can look at the code and it's obvious that it's somewhere here:
int Double(int value)
   return value * value;

Once you have an idea what might be going wrong, start using the debugger to find out why. Put a breakpoint on the first line of the method, and run your app. When it reaches the breakpoint, the debugger will stop, and hand control over to you. You can now run your code line-by-line (called "single stepping") and look at (or even change) variable contents as necessary (heck, you can even change the code and try again if you need to).
Think about what each line in the code should do before you execute it, and compare that to what it actually did when you use the "Step over" button to execute each line in turn. Did it do what you expect? If so, move on to the next line.
If not, why not? How does it differ?
Hopefully, that should help you locate which part of that code has a problem, and what the problem is.
This is a skill, and it's one which is well worth developing as it helps you in the real world as well as in development. And like all skills, it only improves by use!
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Let's start with your destructor, ~Node. If a node follows the one being deleted, it also gets deleted. This means that if you delete the first node, the entire list gets emptied! Is this the intended behavior?

Node's data and next members are public, but the data in a C++ class is usually private. Maybe they're public because the code that handles insertion and deletion needs to modify next. That code, however, should go in a List class template that has the data member Node<T>* first, which points to the first element in the list. Node can then make List a friend so that List--but no other class--can modify next.

The following types of functions would then be provided by List:
// Add ITEM to the end of the list.
void insert(Node<T>& item);

// Remove ITEM from the list and return it. Return nullptr if ITEM wasn't found.
Node<T>* remove(Node<T>& item);

// Remove ITEM from the list and delete it. Return false if ITEM wasn't found.
bool erase(Node<T>& item);

// The function that you're implementing.
Node<T*> deleteMiddle();
List might also provide functions for counting the number of nodes, traversing the nodes, and so on.
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