adding elements to sorted linked lists

Question

I'm working on single linked lists in which I got a problem with add function which adds integers into sorted way. But my program keeps crashing. I've been working all the night but I couldn't find the problem. Does anyone has any idea about this?

Thank you

template<typename T>
class SLList
{
private:
struct Node
{
Node(const T& val= T(), Node* next_ptr=NULL) : data(val), next(next_ptr) { }
// data members
T data;
Node *next;
};
 template<typename T>
void SLList<T>::add(const T& val)
{
 if (find(val)==false)
 {
 Node *curr= head;
 Node* prev=NULL;
 if(head->next==NULL)
 {
 cout<<"head";
 Node *tmp=new Node(val,head->next);
 head->next=tmp;
 return;
 }
 else
 {
 while(curr->data < val && curr!=NULL)
 {
 curr=curr->next;
 prev=curr;
 cout<<"add";
 }
Node *tmp=new Node(val, prev->next);
//head->next=tmp;
 }
}
} `

• Luchian Grigore: If you've been working all night, I'm sure you don't mind telling us where it crashes, or showing the code for Node.
• nullPointer2: struct Node { // constructor Node(const T& val= T(), Node* next_ptr=NULL) : data(val), next(next_ptr) { } // data members T data; Node *next; }; public: SLList(); SLList(const SLList & lst2); ~SLList(); const SLList& operator=(const SLList & rhs); int size() const; void print() const; bool find(const T& val) const; void add(const T& val); void remove(const T& val); private: Node *head; }
• nullPointer2: Node is the copy constructor and it crashes in while loop.
• Luchian Grigore: Please add the code to the question (click on edit).
• nullPointer2: I added the code. Could you please check?

Answer 1

The while exit condition is inverted:

while(curr->data < val && curr!=NULL)

should be

while( curr!=NULL && curr->data < val )

If curr is NULL, it will crash (well, UB to be exact) before it checks for NULL.

• nullPointer2: It still crashing in the same while loop.
• nullPointer2: I have no idea but its going to while loop
• Luchian Grigore: @user1141641 use ideone.com to post code that compiles and exibits the problem. Otherwise, there's no way to tell with the amount of information you're providing. If you want help, you have to put some effort in it as well.
• Luchian Grigore: @user1141641 just go to ideone.com, paste your code, choose C++, and then submit.
• nullPointer2: how do we add another application.cpp file for input in ideone?

Answer 2

Also, move prev = curr forward:

while(curr != NULL && curr->data < val) {
 prev = curr;
 curr = curr->next;
 cout << "add";
}

• nullPointer2: It's only adding the first value. It's not adding the remaining values
• Igor F.: You are missing prev->next = tmp; or similar after the while loop.