CODEWITHSUNDEEP
c++linked-list
Kawatare267
Kawatare267

Reputation: 4386

Delete node from Linked List C++

I am working on iterative delete function that deletes node from a linked list, I think that the code is supposed to work fine. But when I can't use "delete" to delete the first Node of the List. The code is: #include using namespace std;

struct Node
{
    int data;
    Node* next;
};

Node* GetNewNode(int data)
{
    Node* newNode = new Node;
    newNode->data = data;
    newNode->next = NULL;
    return newNode;
}

Node* Insert(Node *root, int data)
{
    if (root == NULL)
    {
        root = GetNewNode(data);

    }
    else
        root->next = Insert(root->next, data);
    return root;
}

void Delete_k(Node *root, int k)
{

    int i = 0;
    Node* P = new Node;
    if (k == 1)
    {
        P = root;
        root = root->next;
        delete P;

    }
    else
    {
        for (int i = 1; i <= k - 2; i++)
        {
            root = root->next;
        }
        root->next = root->next->next;
    }
}

void Output(Node* root)
{
    if (root == NULL)
    {
        root = root->next;
    }
    while (root != NULL)
    {
        cout << root->data << " ";
        root = root->next;
    }
}

int main()
{
    int n, a, pos;
    Node* root = NULL;
    cout << "Input your list hear: ";
    cin >> n;
    while (n > 0)
    {
        root = Insert(root, n);
        cin >> n;
    }
    Output(root);
    cout << "\nDelete Pos?: ";
    cin >> pos;
    Delete_k(root, pos);
    Output(root);
}

I have problem in this

void Delete_k(Node *root, int k)
{

    int i = 0;
    Node* P = new Node;
    if (k == 1)
    {
        P = root;
        root = root->next;
        delete P;

    }
    else
    {
        for (int i = 1; i <= k - 2; i++)
        {
            root = root->next;
        }
        root->next = root->next->next;
    }
}

Upvotes: 0

Views: 2773

Answers (1)

user4581301
user4581301

Reputation: 33982

The problem:

void Delete_k(Node *root, int k)

The value at root is pass by reference, but the pointer to it is not.

Result: Delete_k's root is a copy of main's root. Delete_K's root gets repointed and deleted. Main's root now points at garbage memory. End game program.

Solution:

Provide a reference to the root pointer so that it doesn't get copied. 

void Delete_k(Node *& root, int k)

Or return root from Delete_k.

Node * Delete_k(Node * root, int k)
{
    //existing code
    return root;
}

Upvotes: 3

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