What is an efficient algorithm to find whether a singly linked list is circular/cyclic or not? [duplicate]

Answer 1

Try this

/* Link list Node */

struct Node { int data; struct Node* next; };

/* This function returns true if given linked list is circular, else false. */ bool isCircular(struct Node *head) { // An empty linked list is circular if (head == NULL) return true;

// Next of head
struct Node *node = head->next;

// This loop would stope in both cases (1) If
// Circular (2) Not circular
while (node != NULL && node != head)
   node = node->next;

// If loop stopped because of circular
// condition
return (node == head);

}