Given a singly linked list, return a random node's value from the linked list. Each node must have the same probability of being chosen. Example 1: Input ["Solution", "getRandom", "getRandom", "getRandom", "getRandom", "getRandom"] [[[1, 2, 3]], [], [], [], [], []] Output [null, 1, 3, 2, 2, 3] Explanation Solution solution = new Solution([1, 2, 3]); solution.getRandom(); // return 1 solution.getRandom(); // return 3 solution.getRandom(); // return 2 solution.getRandom(); // return 2 solution.getRandom(); // return 3 // getRandom() should return either 1, 2, or 3 randomly. Each element should have equal probability of returning. Constraints: The number of nodes in the linked list will be in the range [1, 104]. -104 <= Node.val <= 104 At most 104 calls will be made to getRandom. Follow up: What if the linked list is extremely large and its length is unknown to you? Could you solve this efficiently without using extra space?