Python实现链表倒序（带头指针）

Posted 2021-01-25 WESWES

class node:
    def __init__(self, value):
        self.value = value
        self.next = None

def reverse(head):
    if head is None or head.next is None or head.next.next is None:
        return head

    if head.next.next.next is None:
        t = head.next.next
        t.next = head.next
        head.next.next = None
        head.next = t
        return head

    pre = head.next
    cur = pre.next
    pre.next = None
    next = cur.next
    while next.next is not None:
        cur.next = pre
        pre = cur
        cur = next
        next = next.next
    head.next = next
    next.next = cur
    cur.next = pre
    return head

def out(head):
    if head is not None:
        while head.next is not None:
            print(head.value)
            head = head.next
        print(head.value)
    else:
        print(None)

if __name__ == "__main__":
    head = node(None)
    pre = head
    for i in range(6):
        pre.next = node(i)
        pre = pre.next
    out(head)
    head = reverse(head)
    out(head)