Linked list length

Challenge

Count the nodes in a singly linked list by walking it from head to tail.

The grader supplies this node type:

typedef struct node { int data; struct node *next; } node_t;

Task

Implement int list_length(const node_t *head) returning the number of nodes in the list. No main — the grader calls it.

Input

head: a pointer to the first node, or NULL for an empty list. The list is properly NULL-terminated.

Output

The node count as an int (0 for an empty list).

Example

list_length(NULL)        ->   0
list_length(1)           ->   1        (a single node)
list_length(1->2->3)     ->   3

Edge cases

• head == NULL returns 0.

Input format

head: pointer to the first node, or NULL for an empty list.

Output format

The number of nodes as an int (0 for NULL).

Constraints

head points to a singly linked list terminated with NULL. No mutation of node pointers or node data.

Starter code

int list_length(const node_t *head) {
    /* TODO */
    return 0;
}

Common mistakes

Dereferencing head without checking for NULL; modifying head->next instead of advancing a traversal pointer.

Edge cases to handle

Empty list (head == NULL), single-node list (head->next == NULL), multi-node chain.