duplicating nodes of a single list in c

Question

i have a single list non-circular without sentinel and i want to duplicate every node of it. For example, i have 7,5,12,16 and i want to have : 7,7,5,5,12,12,16,16 but i can't create it.Below is my function code for duplicate the nodes(other parts of the program are correct).

    int duplicate_list(listT *list_head) {
    listT *current, *new_node;

    for(current = list_head; current != NULL; current = current->next,counter++) {
            new_node = (listT *)malloc(sizeof(listT));
            if(new_node == NULL) {
                printf("problem in new_node\n");
                free(new_node);
                exit(-1);
            }

            new_node->data = current->data;
            new_node->next = current;
    }
    return(1);
 }

Can someone help me?

[Don't cast `malloc()`](https://stackoverflow.com/questions/605845/do-i-cast-the-result-of-malloc). — melpomene, Aug 26 '18 at 13:17
Why return a value at all if the only possible return value is `1`? — melpomene, Aug 26 '18 at 13:22
Read [How to debug small programs](https://ericlippert.com/2014/03/05/how-to-debug-small-programs/) — Basile Starynkevitch, Aug 26 '18 at 13:22

kiran Biradar · Accepted Answer · 2018-08-26T13:34:58.557

0

You are not inserting duplicate new_node in the list, you are just creating the new nodes in loop. Consider below example for your reference.

    int duplicate_list(listT *list_head) {
    listT *current, *new_node;

    for(current = list_head; current != NULL; current = current->next,counter++) {
            new_node = malloc(sizeof(*new_node));
            if(new_node == NULL) {
                perror("problem in new_node");
                exit(1);
            }

            new_node->data = current->data;
            new_node->next = current->next;
            current->next = new_node;
            current = new_node;
    }
    return(1);
 }

edited Aug 26 '18 at 13:34

answered Aug 26 '18 at 13:19

kiran Biradar

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Without any explanation in English, your answer has no interest to a newbie – Basile Starynkevitch Aug 26 '18 at 13:22
Most of my comments also apply to your code. In addition: `perror` automatically adds a `:`, a space, and an error reason to the provided message, so having a `\n` in there probably ends up looking ugly. – melpomene Aug 26 '18 at 13:27

duplicating nodes of a single list in c

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