题目：

题解：

type Solution struct {head *ListNode
}func Constructor(head *ListNode) Solution {return Solution{head}
}func (s *Solution) GetRandom() (ans int) {for node, i := s.head, 1; node != nil; node = node.Next {if rand.Intn(i) == 0 { // 1/i 的概率选中（替换为答案）ans = node.Val}i++}return
}