GeeksForGeeks - Detect Loop in Linked List

link

Problem

Given a linked list of N nodes. The task is to check if the the linked list has a loop. Linked list can contain self loop.

Solution

struct Node
{
    int data;
    struct Node *next;
    Node(int x) {
        data = x;
        next = NULL;
    }


bool detectLoop(Node* head)
{
    // your code here
    while(head){
        if(head->data < 0){
            return true;
        }
        head->data *= -1;
        head = head->next;
    }
    return false;
}

Time Complexity : O(n)