Cycle Length in Linked List

Problem

Find the length of the cycle in a linked list, or 0 when there is none.

values holds the node values and pos is the index the tail links back to, or -1 for no cycle. Use Floyd's tortoise and hare to find a meeting point, then walk the cycle from that point until returning to it while counting nodes.

Return the number of nodes in the cycle.

Hint

Once the pointers meet, walk one pointer around the loop until it returns to the meeting node.

Test cases

case 1

in: [[3,2,0,-4],1]

expected: 3

case 2

in: [[1,2],0]

expected: 2

case 3

in: [[1],0]

expected: 1

case 4

in: [[1,2,3],-1]

expected: 0

case 5

in: [[],-1]

expected: 0

Starter codePython

def cycle_length(values, pos):
    # Your code here
    pass

5 test cases · run your code against them in the editor