Linked List Cycle

Easy

linked-listtwo-pointers

Determine whether a linked list contains a cycle — i.e. some node can be reached again by following next pointers. Use O(1) memory.

Input

Line 1: the list values in order
Line 2: integer pos — the tail connects to the node at this 0-based index (-1 means no cycle). Your function receives only the head; the cycle is already wired.

Output: true or false.

Example 1

Input:

3 2 0 -4
1

Output:

true

Tail connects back to value 2.

Example 2

Input:

1 2
0

Output:

true

Example 3

Input:

1
-1

Output:

false

Run your code against the sample tests, or Submit to run the full suite.

Easy

linked-listtwo-pointers

Determine whether a linked list contains a cycle — i.e. some node can be reached again by following next pointers. Use O(1) memory.

Input

Line 1: the list values in order
Line 2: integer pos — the tail connects to the node at this 0-based index (-1 means no cycle). Your function receives only the head; the cycle is already wired.

Output: true or false.

Example 1

Input:

3 2 0 -4
1

Output:

true

Tail connects back to value 2.

Example 2

Input:

1 2
0

Output:

true

Example 3

Input:

1
-1

Output:

false

Run your code against the sample tests, or Submit to run the full suite.