leetcode206_反转链表

思路

1. pre 记录已反转的链表
2. cur 记录正在反转的链表节点
3. next 记录还未反转的链表

func reverseList(head *ListNode) *ListNode {
    if head == nil || head.Next == nil {
        return head
    }

    pre, cur, next := (*ListNode)(nil), head, head

    for cur.Next != nil {
        next = cur.Next
        cur.Next = pre 
        pre = cur
        cur = next
    }
    cur.Next = pre
    return cur
}