python递归&迭代方法实现链表反转

class ListNode:
 
    def __init__(self,data):
        self.data = data
        self.next = None

def make_list(L):

  head = ListNode(L[0])
    cur = head
    for i in L[1:]:
        cur.next = ListNode(i)
        cur = cur.next
    return head
 

def print_list(head):
 
    cur = head
    while cur != None:
        print(cur.data,end=' ')
        cur = cur.next
 

def reverse_list(head):

    if head==None or head.next==None:
        return head

>head.next
    reverse = reverse_list(head.next)  #假设reverse是head以后的、已经反转过的链表

    tmp = head.next
    tmp.next = head
    head.next = None
 return reverse  #返回新的列表

def reverse_list2(head):
    #print_list(head)
    cur = head
    pre = None
    while cur:
        tmp = cur.next
        cur.next = pre
        pre = cur
        cur = tmp
    head = pre
    return head
 
if __name__ == '__main__':
 
    L = [3,2,7,8]
    head = make_list(L)
 

    print('原始list：')
    print_list(head)
    print('\n')
 

    revere = reverse_list(head)
    print('反转一次的list：')
    print_list(revere)
    print('\n')
 

    print('head is')
    print_list(head)  #发现此时head节点变成了最后一个节点，说明函数是对head这个实例直接作用的
    print('\n')
 
    # print('revere is')
    # print_list(revere)
    # print('\n')
 
    print('反转两次的list：')
    print_list(reverse_list2(revere))