find entry point of loop linked list

findEntry.py

#!/bin/env python3


class Node:
    def __init__(self, data, next=None):
        self.data = data
        self.next = next


def findEntry(root):
    fast = slow = root
    countFast = countSlow = 0

    fast = fast.next.next
    countFast += 2

    while fast != slow:
        fast = fast.next.next
        countFast += 2

        slow = slow.next
        countSlow += 1

    print(countFast, countSlow)

    fast = root
    countDistance = 0
    while fast != slow:
        fast = fast.next
        slow = slow.next
        countDistance += 1

    return countDistance, fast


def main():
    root = Node(-1)
    prev = root

    for i in range(90):
        cur = Node(i)
        prev.next = cur
        prev = cur
        if i == 47:
            entry = cur

    cur.next = entry

    distance, pos = findEntry(root)
    print(distance, pos.data)


if __name__ == '__main__':
    main()