https://leetcode-cn.com/problems/fan-zhuan-lian-biao-lcof/submissions/

func reverseList(_ head: ListNode?) -> ListNode? {
    if head == nil || head?.next == nil {return head}
    var finallNode : ListNode? = nil
    var cur = head
    while cur != nil {
        //將cur的下一個節(jié)點(diǎn)暫存，以便后續(xù)恢復(fù)鏈表遍歷
        let tmpNode = cur?.next
        //將當(dāng)前節(jié)點(diǎn)的next指向finall
        cur?.next = finallNode
        //將finall指向新生成的cur.next鏈表
        finallNode = cur
        //重新回復(fù)cur原生鏈表，繼續(xù)遍歷
        cur = tmpNode
    }
    return finallNode
}