CODEWITHSUNDEEP
c++
Ipawnu43
Ipawnu43

Reputation: 25

LinkedList using initializer_list

So, i'm trying to initialize a LinkedList class using an initializer_list.

template<typename T>
SortedList<T>::SortedList(initializer_list<T> e){
    head_= new Node<T>(*e.begin());

    long intcheck = 0;
    T old;

    for (auto x : e){
        if(intcheck > 0){
            Node<T>* curr = new Node<T>(old);
            if(head_ == curr){
                head_->next_ = new Node<T>(x);
            }
            curr->next_ = new Node<T>(x);
        }

        old = x;
        intcheck = 1;
    }


}

I get a seg fault when trying to print head_->next_ (nothing wrong with my print function)

Upvotes: 0

Views: 1221

Answers (2)

Edward
Edward

Reputation: 7100

I'm assuming that you actually want the SortedList to be sorted. If so, this will accomplish that goal. It bails out early if the initializer_list is empty, but still leaves the object in a rational state.

template<typename T>
SortedList<T>::SortedList(initializer_list<T> e) : head_{nullptr} {
    if (e.size() == 0)
        return;
    auto it = e.begin();
    for (head_ = new Node<T>(*it); it != e.end(); ++it) {
        Node<T> *n = new Node<T>(*it);
        Node<T> *curr;
        for (curr = head_; curr->next_ && curr->next_->data_ < *it; curr = curr->next_) 
            continue;
        if (*it < curr->data_) {
            n->next_ = curr;
            head_ = n;
        } else {
            n->next_ = curr->next_;
            curr->next_ = n;
        }
    }
}

For completeness, here's the destructor I used to test:

template<typename T>
SortedList<T>::~SortedList() {
    while (head_->next_) {
        Node<T> *t = head_->next_;
        head_->next_ = t->next_;
        delete t;
    }
    delete head_;    
}

Upvotes: 1

Jay Miller
Jay Miller

Reputation: 2234

Your code says that head_->next_ will always be it's default value (we can't see the Node constructor so I can't say what that is).

for (auto x : e){
    if(intcheck > 0){
        Node<T>* curr = new Node<T>(old);
        if(head_ == curr){
            head_->next_ = new Node<T>(x);
        }

It's OK do send your initializer list into the for loop this way. If it's empty you will just exit the loop immediately.

However your curr pointer is allocated right there, while your head_ pointer was allocated above. They will therefore never be equal because you are comparing two pointers that you are allocating in the same function.

Upvotes: 0

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