Question

After breaking my head over this for quite sometime, I am looking for help. Maybe I am doing something really silly here. Below is a basic implementation of linkedlist. However, it does not seem to work. Can someone please take a look?

EDIT: By not working I mean its getting in to an endless loop in the else part of the add function.

#include <iostream>

struct node
{
    int data;
    node* link;
};

void add(struct node** list, int i)
{
    //populate a node
    node* tempNode = (node*) malloc(sizeof(node));
    tempNode->data = i; //**This does not seem to initialize data**
    tempNode->link = NULL; //**Same here**

    //check if the list is empty
    if(*list == NULL)
    {
        //create the node
        *list = tempNode;
    }
    else
    {
        while((*list)->link != NULL); //Enters in to an endless loop here because the link is not initialized
        (*list)->link = tempNode;
    }

}

void print(node** list)
{
    node* itr = *list;
    while(itr != NULL)
    {
        std::cout << itr->data << "\n";
        itr = itr->link;
    }
}

int main()
{
    node* linkedList = NULL;
    node** t = &linkedList;
    add(&linkedList, 10);
    add(&linkedList, 20);
    add(&linkedList, 30);
    add(&linkedList, 40);
    print(&linkedList);

}

Answer 1

Your add function is wrong (the else branch). Since (*list)->link doesn’t get changed, it will loop forever. Try this.

void add(struct node** list, int i)
{
    /* .... */
    if(*list == NULL)
        *list = tempNode;
    else {
        struct node *p = *list;
        /* Search for tail. */
        while(p->link)
            p = p->link;

        /* Since p->link is NULL, it's the tail. */
        p->link = tempNode;
    }
}

This inserts in O(n); user786653 has a nice suggestion in the comments.