22. Detect a loop in LL
Given the head of a singly linked list. Return true if a loop exists in the linked list or return false.
A loop exists in a linked list if some node in the list can be reached again by continuously following the next pointer.
Internally, pos is used to denote the index(0-based) of the node from where the loop starts. Note that pos is not passed as a parameter.
Example 1:
Input: head -> 1 -> 2 -> 3 -> 4 -> 5, pos = 1
Output: true
Explanation: The tail of the linked list connects to the node at 1st index.
Example 2:
Input: head -> 1 -> 3 -> 7 -> 4, pos = -1
Output: false
Explanation: No loop is present in the linked list.
Now Your Turn!
Pick the correct output for the given input
Input: head -> 6 -> 3 -> 7, pos = 0
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Constraints:
- 0 <= number of nodes in the cycle <= 105
- 0 <= ListNode.val <= 104
- pos is -1 or a valid index in the linked list