Write a program to detect loop in a Linked List

Floyd’s Algorithm:

This problem can be solved by using two pointers, slow pointer and fast pointer.Both these pointers will point to head of the linked list initially. Increment slow pointer by 1 node and the fast pointer by 2 nodes. If there’s a loop, the fast pointer will meet the slow pointer somewhere.We’ll discuss in next post where they will meet.

struct node
{
    int data;
    struct node* next;
};
void detectLoop(struct node *head)
{
    struct node *slowPtr,*fastPtr;
    slowPtr = head;
    fastPtr = head;
    
    while(slowPtr!=NULL && fastPtr!=NULL && fastPtr->next!=NULL)
    {
       slowPtr = slowPtr->next;
       fastPtr = fastPtr->next->next;
       if (slowPtr == fastPtr)
       {
           printf("%s","Loop Detected");
           exit(0);
        }
    }
}

Time Complexity : O(n)
Space Complexity : O(1)