reverse linked list

反转单向链表 demo

# reverseLinkedList.py
# 2021年9月19日15:43:19 星期日 中秋快乐
class Node(object):
    def __init__(self, item):
        self.item = item
        self.next = None

# a -> b -> c -> D -> None
# d -> c -> b -> a -> None
def reverseLinkedList(head):
    curr = head
    previous = None
    while curr != None:
        tmp_next = curr.next
        curr.next = previous
        previous = curr
        curr = tmp_next
    return previous

class LinkedList:
    def __init__(self):
        self._head = None

    def is_empty(self):
        return self._head is None

    def append(self, item):
        node = Node(item)
        if self.is_empty():
            self._head = node
        else:
            cur = self._head
            while cur.next is not None:
                cur = cur.next
            cur.next = node

    def show(self):
        cur = self._head
        while cur is not None:
            print(cur.item+" -> ", end='')
            cur = cur.next
        print('None')

    def items(self, head):
        cur = head
        while cur is not None:
            print(cur.item+" -> ", end='')
            cur = cur.next
        print('None')

if __name__=="__main__":
    list=['a', 'b', 'c', 'e', 'f']
    link_list = LinkedList()
    for i in list:
        link_list.append(i)

    link_list.show()
    link_list2 = reverseLinkedList(link_list._head)
    LinkedList().items(link_list2)

运行效果

$ python reverseLinkedList.py 
a -> b -> c -> e -> f -> None
f -> e -> c -> b -> a -> None