Inserting into a linked list not working properly - c

Question

I want to add a insert method for my linked list that would insert onto what's already in the linked list (append values).
Here's my code now:
struct node {
char value;
struct node *next;
};
typedef struct node item;
void main() {
InsertChar('a');
InsertChar('b');
InsertChar('c');
}
void InsertChar(char s) {
item *curr, *head;
head = NULL;
curr = (item *)malloc(sizeof(item));
curr->value = s;
curr->next = head;
head = curr;
while(curr) {
printf("%c", curr->value);
curr = curr->next;
}
printf("\n");
}
The problem is that in the console it prints
a
b
c
I need it to print something more like
a
ab
abc
After calling the 3 InsertChar methods in main().
How can I do this?

Answer 1

Your problem is that the head is declared locally in the function, and when you leave the function, you loose it. When you come to the function again, you create it from scratch, etc.
So you need to pass head as an argument to your InsertChar function.
Also, if you want to see a, ab, abc output, you need to add elements to the tail of your list, rather than to the head as you do it now. In order to achieve that, you either need to store a separate pointer for tail or every time traverse to the last element.

Answer 2

You have to be keeping track of the head of your list. E.g.:
struct node {
char value;
struct node *next;
};
typedef struct node item;
item* head = NULL;
item* curr = NULL;
void InsertChar(char s) {
item* c = (item *)malloc(sizeof(item));
c->value = s;
c->next = NULL;
if (head)
curr->next = c;
else
head = c;
curr = c;
for (c = head; c; c = c->next)
printf("%c", c->value);
printf("\n");
}
void main() {
InsertChar('a');
InsertChar('b');
InsertChar('c');
}
This outputs:
a
ab
abc

Answer 3

There are two problems :
The list's is redefined each time the function is invoked.
you should start from the head of the list when you access the list's elements
This should fix your problem :
struct node {
char value;
struct node *next;
};
typedef struct node item;
item * head = NULL; // global
void main() {
InsertChar('a');
InsertChar('b');
InsertChar('c');
}
void InsertChar(char s) {
item *curr, *temp;
curr = (item *)malloc(sizeof(item));
curr->value = s;
curr->next = head;
head = curr;
temp = head;
while(temp) {
printf("%c", temp->value);
temp = temp->next;
}
printf("\n");
}