Detect_Loop_in_linked_list.cpp

/*
Problem Statement:
-----------------
Given a linked list of N nodes. The task is to check if the linked list has a loop. Linked list can contain self loop.

Example 1:
---------
Input:
N = 3
value[] = {1,3,4}
x = 2
Output: True
Explanation: In above test case N = 3. The linked list with nodes N = 3 is given. Then value of x=2 is given which means last node is connected with xth
node of linked list. Therefore, there exists a loop.

Example 2:
----------
Input:
N = 4
value[] = {1,8,3,4}
x = 0
Output: False
Explanation: For N = 4 ,x = 0 means then lastNode->next = NULL, then the Linked list does not contains any loop.

Your Task: The task is to complete the function detectloop() which contains reference to the head as only argument. 
This function should return 1 if linked list contains loop, else return 0.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(1)
*/

// Link --> https://practice.geeksforgeeks.org/problems/detect-loop-in-linked-list/1#

// Code:
class Solution
{
    public:
        bool detectLoop(Node* head)
        {
            bool answer = false;
            Node *slow = head;
            Node *fast = head;
            
            while(fast != NULL && fast->next != NULL)
            {
                slow = slow->next;
                fast = fast->next->next;
                
                if(slow == fast)
                {
                    answer = true;
                    break;
                }
            }
            return answer;
        }
};