Objective

Implement a function that walks a singly linked list and discards every node whose payload matches a reference value, freeing the removed nodes as it goes.

Steps

• Include list.h in your list_filter.c file; it defines the ListNode node type with a void *data payload and a next pointer.
• For each node, call cmp(node->data, ref). When it returns 0, the node is considered a match and must be unlinked and freed.
• Update *begin whenever leading nodes are removed so the caller still sees a valid head.
• If *begin is NULL, the function must do nothing and return cleanly.
• The non-matching nodes must keep their original relative order; only free is allowed on top of pointer manipulation.
• The prototype is void list_filter(ListNode **begin, void *ref, int (*cmp)(void *, void *));.

Objective

Implement a function that walks a singly linked list and discards every node whose payload matches a reference value, freeing the removed nodes as it goes.

Steps

• Include list.h in your list_filter.c file; it defines the ListNode node type with a void *data payload and a next pointer.
• For each node, call cmp(node->data, ref). When it returns 0, the node is considered a match and must be unlinked and freed.
• Update *begin whenever leading nodes are removed so the caller still sees a valid head.
• If *begin is NULL, the function must do nothing and return cleanly.
• The non-matching nodes must keep their original relative order; only free is allowed on top of pointer manipulation.
• The prototype is void list_filter(ListNode **begin, void *ref, int (*cmp)(void *, void *));.