C in 100 Seconds: Linked List Traverse

Linked List — Traverse, Count, Search

Every linked list operation is built on traversal — walking from head to NULL. Here are three useful variations.

Count Nodes

int count_nodes(Node *head) {
  int count = 0;
  Node *c = head;
  while (c != NULL) {
    count++;
    c = c->next;
  }
  return count;
}

Same while loop as print, but increment a counter instead of printing. Returns the total number of nodes.

Search by Value

int search(Node *head, int value) {
  Node *c = head;
  int index = 0;
  while (c != NULL) {
    if (c->data == value) return index;
    index++;
    c = c->next;
  }
  return -1;
}

Walk the list and check each node's data. Return the index when found, or -1 if the value is not in the list.

Get by Index

int get_at(Node *head, int index) {
  Node *c = head;
  for (int i = 0; i < index && c != NULL; i++) {
    c = c->next;
  }
  if (c != NULL) return c->data;
  return -1;
}

Advance exactly index times using a for loop. The NULL check prevents crashing on out-of-bounds indexes.

Student Code

Try it yourself: episode44/traverse.c