def findDuplicate(self, nums):
        f, s = 0, 0
        while True:
            f = nums[nums[f]]
            s = nums[s]
            if f == s:
                break

        t = 0
        while t != s:
            t = nums[t]
            s = nums[s]

        return t
Condition for convert the array problem to linked list problem:
dataset/ETHPy150Open algorhythms/LeetCode/287 Find the Duplicate Number.py/Solution.findDuplicate