Python实现单链表中元素的反转

class Lnode:
    def __init__(self, elem):
        self.elem = elem
        self.pnext = None
 
def reverse(head):
    if head is None or head.pnext is None: #如果输入的链表是空或者只有一个结点，直接返回当前结点
        return head
    pre = None #用来指向上一个结点
    cur = newhead = head #cur是当前的结点。newhead指向当前新的头结点
    while cur:
        newhead = cur
        temp = cur.pnext
        cur.pnext = pre #将当前的结点的指针指向前一个结点
        pre = cur
        cur = temp
    return newhead
 
if __name__=="__main__":
    head = LNode(1)
    p1 = LNode(2)
    p2 = LNode(3)
    head.pnext = p1
    p1.pnext = p2
    p = reverse(head)
    while p:
        print(p.elem)
        p = p.pnext

class LNode:
    def __init__(self, elem):
        self.elem = elem
        self.pnext = None
 
def reverse(head):
    if not head or not head.pnext:
        return head
    else:
        newhead = reverse(head.pnext)
        head.pnext.pnext = head #令下一个结点的指针指向当前结点
        head.pnext = None #断开当前结点与下一个结点之间的指针指向联系，令其指向空
        return newhead
 
 
if __name__=="__main__":
    head = LNode(1)
    p1 = LNode(2)
    p2 = LNode(3)
    head.pnext = p1
    p1.pnext = p2
    p = reverse(head)
    while p:
        print(p.elem)
        p = p.pnext