Insert a linked list into another linked list

Question

I have a linked list comprised of chars like so...

node1 - "p"
    node2 - "o"
        node3 - "p"

I need a function that will take in three perameters...

node *replaceChar(node *head, char key, char *str)

Stipulations of this function. head is the head of the list, 'key' and 'str' are guaranteed to contain alphanumeric characters only (A-Z, a-z, and 0-9). str can range from 1 to 1023 characters (inclusively).

So if I call this function with these perameters..

node *head == /*the head of the list to be examined*/

char key == "p"

char *str == "dog"

The new list will look like this...

node1 - 'd'
    node2 - 'o'
        node3 - 'g'
            node4 - 'o'
                node5 - 'd'
                    node6 - 'o'
                        node7 - 'g'

All instances of 'p' were replaced with 'dog'

I have a toString function which takes in a string and converts it to a linked list and returns the head. So assume that you can call the function on str = "dog" so...

toString(str) == /*this will return the head to the list made from the str*/

If it's unclear what my question is...I am stumped on how to write the replaceChar function the one that takes in three perameters.. I can create a new list using the string and find all instances of key but making the new list fit into the old list without losing the pointers is killing me.

I HAVE TRIED THIS...

while(head->data != NULL)
    {
        if(head->data == key)
           { 
               node *newListHead = toString(str);

               head = newListHead;

               /*here I lose track of the old list*/

Answer 1

You can start like this:

node *replaceChar(node *head, char key, char *str) 
{
    node *cur, prev;
    for (cur = head, prev = NULL; cur != NULL; prev = cur, cur = cur->next)
        if (cur->ch == key) {
            node *hstart = toString(str);
            for (node *hend = hstart; hend->next != NULL; hend = hend->next)
                ;
            if (prev == NULL)
                head = hstart;
            else
                prev->next = hstart;
            hend->next = cur->next;
            free(cur);
        }

}

My assumptions: Your node struct is like:

sturct node {
    char ch;
    struct node* next;
};

toString(str) works perfectly fine.