How do you write a void function to delete all nodes in a doubly linked list?

Answer 1

void delete_all (list* lst) {

if (!lst !lst->count) return; // sanity check!

while (lst->count) { // repeat until the list is empty

node* tail = lst->tail; // store the current tail

lst->tail = tail->prev; // set the new tail

if (lst->tail) lst->tail->next = NULL; // detach the old tail from the new tail (if there is one)

else (lst->head = NULL); // if there is no tail then here can be no head either

free (tail->data); // release the old tail's data

free (tail); // release the old tail

lst->count--; // update the count

}

}

The above function assumes your list uses the following C-style structures:

typedef struct node_t {void* data; node* next; node* prev; } node;

typedef struct list_t {node* head; node* tail; unsigned count; } list;