Given `head`, the head of a linked list, determine if the linked list has a cycle in it.
There is a cycle in a linked list if there is some node in the list that can be reached again by continuously following the `next` pointer. Internally, `pos` is used to denote the index of the node that tail's `next` pointer is connected to. **Note that `pos` is not passed as a parameter**.
Return `true` *if there is a cycle in the linked list*. Otherwise, return `false`.
Examples
Example 1
Input:
head = [3,2,0,-4], pos = 1Output:
trueThere is a cycle in the linked list, where the tail connects to the 1st node (0-indexed).
Example 2
Input:
head = [1,2], pos = 0Output:
trueThere is a cycle in the linked list, where the tail connects to the 0th node.
Example 3
Input:
head = [1], pos = -1Output:
falseThere is no cycle in the linked list.
Constraints
- •
The number of the nodes in the list is in the range [0, 10^4]. - •
-10^5 <= Node.val <= 10^5 - •
pos is -1 or a valid index in the linked-list.
Code Editor