我正在尝试解决这个问题：https://leetcode.com/problems/reverse-linked-list/description/?envtype=study-plan&id=level-1

输入：head = [1,2,3,4,5]

这是我的代码：

func reverseList(head *ListNode) *ListNode {
    var prev *ListNode
    prev = nil
    for head.Next != nil {
        head, head.Next, prev = head.Next, prev, head
    }
    if head.Next == nil {
        head.Next = prev
    }
    return head
}

运行后，程序报错：panic: 运行时错误: 无效的内存地址或 nil 指针取消引用。 请向我解释为什么会出现此错误

输入：head = [1,2,3,4,5]。我希望循环 4 次，直到 head.next == nil。但出乎我意料的事情发生了。

正确答案

如果 head 是 nil -> head.next 将出现像您给出的错误

func reverselist(head *listnode) *listnode {
    var prev *listnode
    prev = nil
    for head != nil && head.next != nil {
        head, head.next, prev = head.next, prev, head
    }
    if  head != nil && head.next == nil {
        head.next = prev
    }
    return head
}

更简单的是：

func reverseList(head *ListNode) *ListNode {
    var prev *ListNode
    prev = nil
    for head != nil {
        head, head.Next, prev = head.Next, prev, head
    }
    if head == nil {
        head = prev
    }
    return head
}